I really don't get the MMO RPG appeal, maybe it's just that I played the wrong ones, but I've seldom been so miserable as when I tried to play an MMO RPG with friends.
Namely Runes of Magic and Age of Conan. Path of Exile to a certain degree, too.
Runes of Magic: Terrible GUI, combat that is literaly just "click on enemy and then press puttons 1-10 in order over and over until the target dies". One of the most annoying things, you had a bag in your inventory that couldn't be dropped or sold, it contained a bunch of potions, some gems or whatever... and another bag that would unlock on the next level. Surely enough, it contained potions and stuff and another locked bag that would be unlocked when you reach the next level... and so on. That felt like the most desperate attempt to sucker people into the game, by showering them with a shitton of useless crap (I literally never used any of those potions and I couldn't even be bothered to look up what the other items do).
The quests were utterly terrible "Kill 10 wolves" and of course, they only stand around in groups of 4... anything with a "get X of Y" quest had this setup. Annoying as fuck and it's just broing busywork. Adding a layer of "walking in circles, hoping for a new group of Y to pop up" is mind numbingly boring.
A friend of mine obsessed over this game and spent days grinding stuff to unlock and upgrade a guild-hall, that literally no one from outside the guild could even see.
Age of Conan wasn't much better, the combat wasn't as terrible, but overall, it still had one of my MMO pet-peeves on full display: Enemies that just stand around in small flocks, waiting to be killed. Wouldn't even be that bad if their agro-range wasn't so comically small. There's just a bunch of barbarians standing around, with their thumbs up their ass, until you approach closer than 10 feet and they go into full rage mode. I like games for the immersion, and this breaks immersion immediately. Doesn't help that the quests are of the aforementioned "kill x amount of Y" types with "walking around until you find enough Y" shit.
I was outright miserable trying to find enjoyment in this game, hoping it'll become more fun at some point. But nope. Only played it like 3 days and the most fun I had was on the last day, when my friends and me did some quests together, after like the 2nd or so, I just stopped giving a fuck and went along with them without even taking the quests. At the end, I trolled them by shooting pillars that they needed to destroy and the game wouldn't recognize the quest as being finished if someone without the quest destroyed them, so they had to wait for them to respawn.
The only time I was equally miserable in a game was when we played Borderlands 2 (I think) in coop mode with 4 players. Every enemy was an absurdly hard to kill bullet-sponge, there was a shitton of loot getting dropped all over the place (and the "Oh look a better gun!" dopamine rush ends, when that shit happens every 5 seconds and the enemies still take a minute of concentrated fire by the entire party to die). FFS, I played that game for about 90 minutes and uninstalled it. The humor and constant QUIRKAAAAAY dialogue pissed me off, too.
Another pet-peeve that kills any interest, especially in FPS games: Pop-ups for XP, damage, hitpoints and so on. I think CoD does this, where you shoot a guy and your screen gets cluttered with popups announcing you shot some wanker in the dick for a tripple double extra XP boost for the next 25,3seconds or whatever the fuck that clusterfuck on the display is supposed to mean. I don't care if it's somewhere in the periphery, but when it pops up in the middle of the screen, it's just annoying as fuck. Doesn't help that the entire attitude towards gaming that this stands for is utterly toxic to me.