The core gameplay loop can be boring if you only do one thing, such as grinding mobs.  Set aside that "fun" and "boring" are largely subjective statements, and I can agree -- if someone simply grinds mobs and does nothing else, the game can get boring.  Keep in mind, though, that BDO is a grinder -- all MMO's are grinders, to varying degrees, with different styles of grind.  BDO is on the more "hardcore" grind side of things, especially if you're chasing big goals.  Goals, though, are self-set and self-achieved -- in that, you don't need much gear to enjoy the game's content and there's high emphasis on personal agency (not relying on others).  You only need gear for PVP with the top guilds / players.  PVE = don't need gear to steadily progress.  PVP = tons of gear capped content, including T1's, 2/3 castles being gear capped, and Arena PVP.  The ONLY reason you need high gear -- the gear that I'm talking about -- is for high end PVP -- which participation is 100% voluntary.  Can't even cry about Open World ganks anymore because those are so far and few these days with the MANY ways to avoid OWPVP now.  And about PVP's technical shortcomings, I mean, yeah, they exist, but to which degree -- TO ME -- it's just sounds like an excuse to avoid getting good.  Unless your internet is that bad, anyone with gear + skill can do well in PVP.  But yeah, there are issues and it's good those technical issues are pointed out.  But to me, IDK how to explain, it just sounds like an excuse or personal, mental roadblock.

The "fun" to me, about BDO, is setting goals and achieving them as the bottom line.  This, at least to me, is the MAIN content in BDO -- setting and achiveing goals.  I purposefully put that as a broad statement because the game has many things to go for, being sandbox-based.  There's many goals and things to do in BDO, so I find it unlikely that someone will only do one thing like grind mobs for the entirety of their gameplay.  If someone ONLY grinds mobs and nothing else, given the diversity of things to do and go for, then I can see it being "boring".  Which is why I keep my goals in multiple areas (and play other games from time to time lol).

Breaking up the monotony is key for long time play, however, me personally, all I do is grind mobs, PVP, and just got back into training horses.  It's cozy.  And I steadily progress towards my goals.  I play other games too, my group-fix is playing other games with my IRL friends.  BDO is my personal space, though I have a couple friends who play too.  I also enjoy a good single player story driven game.  But BDO is where I settle in and get cozy for most of my gaming time these days and I'm still hungry for better gear.  Mostly because I enjoy it.

About the hardcore/long-haul grind for top-shelf items, that's the way BDO has always been -- the BEST items always being a hardcore grind to get, or getting extremely RNG carried (high risk, high reward).  That's just how it's set up -- the BEST items require the most grind or luckiest RNG -- no way around that.  To me, it's good because there will always be a reason and purpose.  Instead of floundering around waiting for the next expansion to drop like in other MMO's.  I also like the feeling of achieving those lofty goals.  Have you ever built a Carrack?  I haven't.  But the people I know who did, who love their Carrack and the immense pride they have with it (though it sucks there isn't much ocean content, from what I heard).  I am currently grinding for a PEN Turo's Belt and need about 50ish bil more.  I'm about half way there, and in about a month or so, I should be there.  Once I get that, it's gonna be awesome -- but it doesn't stop there -- I have a gear goal after I get the V Turo to push my gear in another direction >> moving to a DR build with 316 AP/317 AAP/ 401 DP with a second accuracy accessory.  And after that BIG-D gear, I have yet ANOTHER gear goal.  And after that, you guessed it -- more gear goals.  Never ends.  Always something to go for.  If gear were easy, what are you gonna do with it anyway?  Grind more mobs?  The same grind you say is boring?  PVP?  Will there be more GVG around?  Because so much PVP is gear capped these days.

Bottom line is -- IMO setting and achieving goals is the "fun".  The grind:  just part of the journey and, as the motto goes, "The Adventure Never Ends".  I like that.

I've found a nice home in BDO where I can log in, do something familiar in which I'm comfortable with, and make steady progress.  It's also great that my progress is on me and no one else, and I can play towards my goals at 100% my own pace, whereas other MMO's lock you into time-gated dailies or forced group content.  It's the only MMO that has held my long-term interest... and I lend that to how BDO is structured -- In that, my goals (mainly gear) is something that I'll always be playing towards (being that I refuse to P2W Crons, silver for outfits, and gamble on very expensive accessories) and I can play towards it at my pace. 

This is not sunk cost, I assure you.  It's just the best MMORPG out right now to me.  I don't find the same level of passion I find in BDO, not sure how else to explain it.  Game feels familiar, I love the way Sorc feels, I love my guild, and I get hard-ons when I look at my gear, making me want better gear, not sure how else to explain my interest in the game, but it's not sunk cost to say I'm actually passionate about my time here.

Don't like BDO's style?  Then you don't like it.  I'm not going to be the one to change your mind.  It's got its good parts and bad, it's up to you to determine what you like, not me or anyone else.  This is just my experience that I share with you.  Though, I do look forward to Ashes of Creation for a Trinity-based PVE and PVP experiences to scratch that itch since BDO classes are designed, mostly, with self-sufficiency in mind.

You forgot the brutal RNG gambling enhancment system.