Same here. And they all go "but progress and getting loot is fun"..Except, once again, you don't need BiS to kill the boss.
Literally no boss in the entirety of WoW has REQUIRED BiS to kill the boss. If you're getting benched for not having a trinket, find a guild that doesn't suck because that kind of arbitrary nonsense gets nobody anywhere.
And because that still doesn't answer the question, here it is again: Why does caring about a trinket matter whatsoever? I can not care about a trinket and still get it, that doesn't mean I care any more about it.
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People have forgotten that the game isn't just numbers on a spreadsheet and it really upsets me. This is the reason I don't enjoy the game anymore - I used to raid lead in Wrath, wasn't super good back then but we did normal mode ICC 10 man and managed to get Lich King before Cata launch which I was proud of.
My raid group was entirely made of friends. Yeah, we fucked about and pulled extra trash and laughed and had fun. I was a SUPER lore nerd then, so I made sure to have relevant jokes ready for every boss pull and every ability, we all had a blast.
I tried doing the same thing in WoD for Blackrock Foundry. Couldn't get people to laugh whatsoever. All people cared about was their place on the damage/healing meters. I called the raid after 4 bosses cause I was just so disappointed and it just wasn't fun.
Since then fun has been the only thing I look for in game.