Um.  They won't slow the game down, ever.  BDO has had this type of fast action combat since day 1 and it is this game's shining achievement.  You're new and by reading this post it's clear to me you aren't very experienced.  Maybe the only PvP you've experienced is seasonal PvP with other inexperienced PvPers, so it makes sense that it's inexperience talking here.

Fast action combat -- this is what BDO is known for.  This isn't ESO, Lost Ark, or Guild Wars.  It's fast by design.  Classes have great movement, lots of abilities, lots of AoE -- every class has these things.  That's the beauty of BDO combat -- and it requires control.  To gain control and succeed in PvP (especally against knowledgeable PvPers), it requires intricate knowledge of your class, how other classes work, the CC system, and situational awareness.  Think of it like fighting games -- take Street Fighter for example.  You can "button mash" (press random stuff) if you're inexperienced. But if you're good, you use your abilities with timing, precision, and knowledge.  You bait your opponent in order to punish them.  You look for mistakes your opponent makes to punish them.  You avoid making mistakes so you don't get punished.  It's just like this in high level PvP in BDO.  If you "roll your face" in BDO, you won't stand one millisecond against high level PvPers.  It's clear to me you're a "button masher", if we're speaking in Street Fighter terms, by saying this, which is OK since you're new.  It's OK since I can explain.

You say the PvP core mechanics are too simple because all you need to do is catch a CC and burst.  But answer me this -- HOW do you catch a CC in the first place? 

In BDO, there is always a "dance" before the CC.  Where both players are jousting -- using the Super Armor, Frontal Guards, and Stamina bar to avoid CC -- while simultaneously trying to land a CC of their own on their opponent who is doing the exact same thing.  Against high level PvPers, this dance is intricate and complex --  It is very easy to see a good PvPer from a bad one, very, very easy to see.  Just like in Street Fighter. 

In Street Fighter, there's something called "footsies" = a fundamental aspect where spacing, hit confirms and whiff punishes are key to victory.  It's similar to the dance in BDO = you "dance" (footsies) by managing space, knowing when to use what ability to land CC, what kind of CC is landed (there are multiple types of CC, each with different effects.  IE:  If you land a "Stun" CC, you can follow up with a "Stiffness" CC, followed up by a "Floating" CC, and end with an "Air Smash" CC to maximize the CC combo), knowing the CC Count of the CC's applied, the CC animations on your opponent to quickly determine what kind of CC is inflicted, and more.  Knowing CC Counts, CC timers, CC entended combos, animations of CC, your class' abilities and what CC's your abilities do, and how CC Effects function with other CC Effects, all of this need to be factored in within seconds during a fight, even milliseconds.  In many cases, especially when gear is not potato, a single second could mean the difference between life or death.  The CC system by itself is complex and takes time to master and practice.

Learn this chart and make it your bible:

Not only do you need to learn about CC Effects, CC Count, CC Count manipulation (to maximize CC potential), you ALSO need to know your class' protections and other class' protections.  Protections prevent CC, so if you use any CC ability against someone who is in Super Armor or Block, your CC will not land, rendering your ability on cooldown, at times leaving a gap that you can then be punished for.  Again, you need to not only know about CC system - but also YOUR class' mechanics and OTHER class' mechanics to be truly successful in PvP.

You can turn down the Effect Opcaity in settings if the VFX is too much.  It also increses frame rate, so for beginners, I'd say lower it enough that it doesn't bother you, but enough so you can still see AoE's and projectiles while you're still learning how classes work and the class' animaitons.  After a while, you can turn the opcacity very low, or even completely off, to increse frame rate because you know the animations character models do in each of their abilities, and what the abilities are. Personally leave the effects very low as preference, but I know people who turn them completely off.

To a newbie, the combat may look chaotic.  But that's the nature of BDO combat -- it's fast and flashy, so to the ignorant, it looks crazy.  With so many abilities at your disposal, it may seem as if you're "button mashing" to win, like how a new player in Street Fighter would do, pressing random buttons hoping it works.

^ New Street Fighter player / BDO PvPer.

This is not the case in high level BDO PvP -- even mid level where players start to grasp the game.  I'm not the best, but have been PvPing in BDO since day 1.  After 5+ years of playing Sorceress, I still find myself learning something new almost every day I PvP.  Things like spacing, deeper matchup knowledge, new ways to extend CC, etc., I'm always learning something new.  To me, that is a testament to how deep the combat in BDO can get -- after years, I'm still improving.  That wouldn't be the case if "random BS go" was actually a thing.  But I do PvP against people who know what they're doing, maybe you need to PvP against better players, IDK.

Um.  They won't slow the game down, ever.  BDO has had this type of fast action combat since day 1 and it is this game's shining achievement.  You're new and by reading this post it's clear to me you aren't very experienced.  Maybe the only PvP you've experienced is seasonal PvP with other inexperienced PvPers, so it makes sense that it's inexperience talking here.

Fast action combat -- this is what BDO is known for.  This isn't ESO, Lost Ark, or Guild Wars.  It's fast by design.  Classes have great movement, lots of abilities, lots of AoE -- every class has these things.  That's the beauty of BDO combat -- and it requires control.  To gain control and succeed in PvP (especally against knowledgeable PvPers), it requires intricate knowledge of your class, how other classes work, the CC system, and situational awareness.  Think of it like fighting games -- take Street Fighter for example.  You can "button mash" (press random stuff) if you're inexperienced. But if you're good, you use your abilities with timing, precision, and knowledge.  You bait your opponent in order to punish them.  You look for mistakes your opponent makes to punish them.  You avoid making mistakes so you don't get punished.  It's just like this in high level PvP in BDO.  If you "roll your face" in BDO, you won't stand one millisecond against high level PvPers.  It's clear to me you're a "button masher", if we're speaking in Street Fighter terms, by saying this, which is OK since you're new.  It's OK since I can explain.

You say the PvP core mechanics are too simple because all you need to do is catch a CC and burst.  But answer me this -- HOW do you catch a CC in the first place? 

In BDO, there is always a "dance" before the CC.  Where both players are jousting -- using the Super Armor, Frontal Guards, and Stamina bar to avoid CC -- while simultaneously trying to land a CC of their own on their opponent who is doing the exact same thing.  Against high level PvPers, this dance is intricate and complex --  It is very easy to see a good PvPer from a bad one, very, very easy to see.  Just like in Street Fighter. 

In Street Fighter, there's something called "footsies" = a fundamental aspect where spacing, hit confirms and whiff punishes are key to victory.  It's similar to the dance in BDO = you "dance" (footsies) by managing space, knowing when to use what ability to land CC, what kind of CC is landed (there are multiple types of CC, each with different effects.  IE:  If you land a "Stun" CC, you can follow up with a "Stiffness" CC, followed up by a "Floating" CC, and end with an "Air Smash" CC to maximize the CC combo), knowing the CC Count of the CC's applied, the CC animations on your opponent to quickly determine what kind of CC is inflicted, and more.  Knowing CC Counts, CC timers, CC entended combos, animations of CC, your class' abilities and what CC's your abilities do, and how CC Effects function with other CC Effects, all of this need to be factored in within seconds during a fight, even milliseconds.  In many cases, especially when gear is not potato, a single second could mean the difference between life or death.  The CC system by itself is complex and takes time to master and practice.

Learn this chart and make it your bible:

Not only do you need to learn about CC Effects, CC Count, CC Count manipulation (to maximize CC potential), you ALSO need to know your class' protections and other class' protections.  Protections prevent CC, so if you use any CC ability against someone who is in Super Armor or Block, your CC will not land, rendering your ability on cooldown, at times leaving a gap that you can then be punished for.  Again, you need to not only know about CC system - but also YOUR class' mechanics and OTHER class' mechanics to be truly successful in PvP.

You can turn down the Effect Opcaity in settings if the VFX is too much.  It also increses frame rate, so for beginners, I'd say lower it enough that it doesn't bother you, but enough so you can still see AoE's and projectiles while you're still learning how classes work and the class' animaitons.  After a while, you can turn the opcacity very low, or even completely off, to increse frame rate because you know the animations character models do in each of their abilities, and what the abilities are. Personally leave the effects very low as preference, but I know people who turn them completely off.

To a newbie, the combat may look chaotic.  But that's the nature of BDO combat -- it's fast and flashy, so to the ignorant, it looks crazy.  With so many abilities at your disposal, it may seem as if you're "button mashing" to win, like how a new player in Street Fighter would do, pressing random buttons hoping it works.

^ New Street Fighter player / BDO PvPer.

This is not the case in high level BDO PvP -- even mid level where players start to grasp the game.  I'm not the best, but have been PvPing in BDO since day 1.  After 5+ years of playing Sorceress, I still find myself learning something new almost every day I PvP.  Things like spacing, deeper matchup knowledge, new ways to extend CC, etc., I'm always learning something new.  To me, that is a testament to how deep the combat in BDO can get -- after years, I'm still improving.  That wouldn't be the case if "random BS go" was actually a thing.  But I do PvP against people who know what they're doing, maybe you need to PvP against better players, IDK.