This chat has become the guildquest chat request/announcement because you can't do anything the right way. Even guildquests have rng and as players want to do specific ones, they spam what they want or what they see.
Sailing groupchat was one of the nicest ones and it turned into shit.

Just fix it by changing the way guilds can pick guildquests: make a damn list of all quets and guilds can pick whatever they want in whatever size whenever they want. 
Or create a groupchat for guildquests...
2 easy simple solutions!

Does this shit have any sense?

pick any GQ with limit of 10 will result in my doing 4 in 2 hours and me alone.

Not sure if i understand what you are saying as i'm not a notive english speaker. 
Do you mean: no one is interested in guildquests so you have to them alone?

The easiest fix for guild quests is making a dedicated groupchat for that.
The best fix would be guildquest rework. one can dream.
Just imagine being able to pick the quest you feel like doing whenever you want instead of begging/hopping servers to find what you look for. I believe no one accepts random guildquests anyway.

I got the answer for you why they dont!

They want you to stay in the game for as long as possible, you can believe me or not it is up to you.
Allowing any quest to be picked up at any time will remove the time used looking for it, which is why they implement rng in all the aspects of the game.
Having a different channel for Guild missions in their eyes(PA) would make no sense, this has become a thing due to quests being so random driving the players create the need for it.
I am not saying the way it works right now is okay, plus if i need to count active sailors/fishers in chat...one hand would suffice.
There is probably more that can be said for the topic, cant think of more of it atm.