I guess it comes from a background of playing pen and paper D&D, but I always hated the trinity. It's a super dumbed down version of how D&D combat actually works and the roles you have there in.
For instance, in real D&D, clerics are badasses. They don't sit around on the back line waiting to heal people. They're right up with the fighter, smashing heads in. Clerics in D&D are in the thick of things, not cowering in the back waiting to pop heals. At high levels, they are as powerful or even perhaps more (in certain ways) than high level wizards.
Speaking of wizards, they aren't just "dps" in real D&D either. They were your ace in the hole (or for Malazan fans, shaved knuckle in the hole). You're all fucked? Wizardbro has your back with stuff you didn't even know existed.
For that matter, thieves/rogues are not just "dps" either in real D&D. Finding secret passages, unlocking doors and disabling traps were essential things, and formed the real identity of that role in D&D. And instead we get none of that, just "dps".
Lastly, no dungeon master worth a shit would ever made real D&D combat play out how it the "trinity" does in MMOs. Players would be dumping their pizza and drinks on him/her in minutes.
No, combat wasn't "everyone automatically attacks the tank and no one else" in D&D, because that is boring tripe.
Yes, your fighter was on the front lines, usually going toe to toe with a troll or a golem or something, and wizards stayed out of melee, but that wasn't the extent of combat, nor was your cleric just sitting there healing and doing literally nothing else the entire fight.
No, fights were much more involved than the simplistic "trinity" with threat-based AI.
Fighters usually "tanked" the big enemies that could crush your wizard, yes, but you also had enemy wizards, rogues etc. which people had to deal with, and it wasn't a matter of the fighter just fighting everything himself aside from ranged.
I am soooo glad to see this system finally die, it wasn't ever fun or good in any way IMO, just a half assed implementation of half of the real D&D roles.