One of my favorites that I fell in love with was a particular class on an MMO game called Rift. It was the chloromancer. In practice it was tricky and arguable how effective it is but it was a healer class that provided raid/group heals by doing damage. Your damage attacks would provide the heals.

Just a neat concept I immediately fell in love with.

I hate stealth. I want to go everywhere guns blazing. This is what ruined the Farcry series for me. Having unskippable stealth sections.

I mostly play turn based JRPGs. My main gripe with any video game is excessive interacting with menus and inventories. I want to play a game, not enter submenus of submenus to change minute things. So here's some features to combat that:

Queues: lining up research or skills to learn, so I don't have to enter the fucking menus after every battle/minute.
Skill/Equipment sets: let me save my setups. Give me a few slots, and a warning if some part of that setup is used by another character. Heck, give me a way to save whole party setups, so I can have e.g. fire-killer team of ice-themed abilities on all characters. Or just have a standard ability set for progression and a second, temporary one for skill learning or whatnot.

Chained Echoes and FFVIIR had some good QoL improvements, but how many times do I have to shuffle materia or accessories, just because I'm leveling something? Every second encounter, because something is maxed and I have to swap it out for something else?

And Inventory management, that can make or break a game. Some of those submenus take half a minute to enter before you even do anything. Astria Ascending (I don't recommend) was awful in that regard and guilty of everything mentioned above.

Fucking menus man... Give me some elaborate customizable skill setup slots and queues, please.

I hate anything that stops me from playing the game. Stun mechanics, usually, but I also include quick time events.

The one that sticks in my mind was those dumb water mages in genshin impact. They trap you in a bubble and hold you there for a few seconds. If it's an intense enough fight, a few seconds is an incredibly long time, and you're just sitting there watching the game happen and you've lost your agency. It's worse for me because I had built shields and healing into my team to shore up my shortcomings with dodging. It felt clever, but them the game sends in this mechanic which invalidates my solution.

With quick time events, I just get annoyed at the genre switch. Don't get me wrong, there are cool enough cinematics out there... It's just... Like usually I'm watching these and thinking, "wow, that would've been fun to do, you know, myself."

Nevermind that I'm too ADHD. Like I have cats and a partner and a phone. If I get a buzz or whatever else, I might miss the prompt. Or if I ignore the buzz, whatever that might have been can sometimes get discarded in my brain.

@MJBrune I think I really like timed challenges even if I'm not very good at them.

Like block -> parry

Also with tolerance areas where you can hit a "passing" "good" or "perfect" score.

Combos. I don't like them when they're intentional by the developer, they need to be something that you feel like you've discovered on your own. I hear Baba is You is pretty good about that.

I recently observed a game of MtG where a newish player was playing a scry deck, some premade or something, had a guy who would scry every time a creature dropped, and a guy who would place counters every time he scried. He'd edited the deck slightly, added a creature that spawned tokens every time it received counters. Managed to get them all out at once before realising what he'd done; straight up had to ask if tokens count as creatures dropping because he wasn't sure if infinite combos were real. That's a good feeling, because it's something he did, not something that was given to him.

Contrast League or Overwatch or whatever where the devs have specific ideas about how characters should work and will aggressively destroy things outside of that. Or just modern Magic.

Forced sections in AAA games. If you wander left or wander right or jump or sneak a direction it didn't want you get a mysterious death. Just make it a cutscene if you are going to pidgeonhole me so much assasins creed, or a cartoon movie.