Gaming

Squad/micro-strategy mechanics in fps games. Commanding npcs to do specific things in the middle of a gunfight isn’t fun. Bonus points if the npc ai gets in your way when you're not fighting as well.

Bad tutorials. Don't teach me the game mechanics that could be learned in-game in an environment different from the rest of the game. Also dislike sudden lore dumps after the tutorial.

Mechanics in games where they don't belong. Not every game needs skill trees, not every game needs stories or lore.

Unrepairable weapons are the worst thing. There's nothing worse than finding a super cool, rare weapon and being paranoid about it breaking.

Loot

I hate collecting it, managing inventory, selling it, crafting it, and so on. I used to love it, but these days I much prefer a more guided experience where the only items I get are interesting. Elder Scrolls completely destroyed this whole mechanic for me because I'm a bit obsessive and would try to bring literally every plate back to town to sell.

As a corollary, I'm not a fan of dealing with shops in general. I'm fine if they exist, but I really think the game should supply you with everything you need to complete the game, and shops should be a backup plan, not a core mechanic.

non-renewable consumable items.

using consumables is hard enough, but you're telling me there's a finite number of these? forget it.

only exception is rougelikes.

Escort missions

I hate RNG-heavy progression that discourages playing the actual game.

Path of Exile had terrible loot droprates and gamble crafting when I last played in Ritual League. Starting a league = poring YouTube for safe league starter builds to follow step by step. Gearing up = only picking up currency and buying items from other players on a website. Making $$$ = flipping items (buy low sell high) in hideout (personal town).

Path of Champions (PvE gamemode in Legends of Runeterra) drops shards and fragments to unlock new champions and relics that add a passive effect. Drops are random and not duplicate protected. Champions need 2 star upgrades totalling their unlock cost to feel playable. Optimal progression = speedrunning dailies/weeklies, 2-starring meta champs, and logging out.

The new Gollum game was very impressive in the way it managed to implement so many of the mechanics in this thread

Stamina, why can't i just keep running forever!! Even worst in open world games.

Quick save/quick load. Not as relevant any more, but so many games used to have it. The meta game just became saving at the opportune moment and trying every possible action from there to progress forward.

Blew my mind in the first Bioshock where you could qs/ql, but the vita chambers were forgiving enough to wean you off it.

Perhaps not specifically a mechanic, per se, but save points. I want to be able to save whenever, wherever. I don't always have time to make it to the next save point before I need to stop playing.

Invisible walls, including on high places or on bridges - I get it, possibly it would be less fun if the character dies just because you go a bit off-road, but not everything has to be easy!

Those hints to success "difficult parts". Some games think their players are braindead. If you have some trouble or spend a bit too much time doing a quest or killing a boss, NPCs or game interface constantly yells at us hints to skip those "difficult" parts. Games are more and more aimed for dumb casuals. I'd rather have the satisfaction completing a challenge by myself. Lets not forgot that today's games are increasingly easier and shorter (and pricier) than before...

Perhaps forced online with no way to self host.

Cutscenes for repeated actions like in the Zelda series. Having to dig through the menu to perform simple actions.

Stealth. I hate hiding and creeping around waiting for an NPC to move. It's like, "oh, you want to play the game? How about not playing the game instead?" Infuriating.

Grinding to advance and make the game easier.

Looking at you fdev with Elite Dangerous, or Rockstar and GTA.

Having balance and not level locking stuff is hard I get that. And you have people that will burn though content like it’s a free crackpipe. But it basically makes a lot of adults or people that just play games casually or in moderation just not fun

I'm not a big fan of fishing mechanics, they're usually shallow "press button at random signal, get a random prize" mechanics.

Also escort missions where the NPC being escorted does not understand that it should protect its own life. I don't mind repeating a mission due to my own mistakes, but I don't want to do it because some AI went potato.

Quick-time events but SPECIFICALLY the ones that give you way too little time to react. Like, I never mind them too much, especially the ones in the Yakuza series, but I remember there was this game on the Wii called Indiana Jones and the Staff of Kings that would throw these inputs WAYY too fast at you.