The biggest problem is that in a lot of games, and even more D&D, that if the player just picks and plays an "average" character they will be super over powered at best, and a full munchkin at worse. All while not "really doing it". This is a game rule problem, and it is a big one.
I mean, that's not true.
Being a munchkin isn't about power level, it's about attitude. Being a munchkin means you don't care about the other players, and you think you can "win" at TTRPGs (primarily by making the game 100% about you/your PC 100% of the time). The usual way they do this is by making broken characters but the power level isn't the defining factor.
Also, what do you mean by "super over powered"? Power exists in a context, it's relative - you seem to be saying the "average" 5E D&D character is "super over powered", but that's obviously nonsensical - if everyone is "super over powered", then no-one is "super over powered".
So you seem to be confusing and conflating a totally different issue here - what appears to be a personal dislike of games that aren't "street level" or "gritty". That's not got anything to do with "optimization".
And almost as bad are the DMs and players that refuse to do anything about the above problem. And most fixes are very easy. Yet many say "all hail the rules" and refuse to do anything.
But what you're describing isn't an actual "problem".
The problem seems to be with you and your own choices.
You're apparently deciding to play RPGs that have tones and power levels you don't like, then you're apparently getting angry that other people aren't willing to house-rule those games to the power level you want, even though none of them signed up for that. I get that you may regard 5E D&D and the like as "super over powered" - presumably meaning that the PCs are "superheroes" in your view. Well - there's an easy fix for that - don't play those games. Go play something actually gritty like Warhammer Fantasy Roleplay or Call of Cthulhu or DCC something! This is 100% on you. You cannot go around joining games you know don't like the rules/tone of, and then saying "Omg these awful jerks won't house-rule the game to my tastes!!!".
If you can't find a game locally that suits your more niche tastes, you can either run one, or you have to go online. Maybe that's not ideal but it's the way of the world for social games like TTRPGs - you need other people, so you need to find people who like the same things as you. You can't just get mad at people and make them change games to suit you.
Next is the huge problem of unintended consequences. The DM or players comes up with a wacky idea to change the rules for whatever reason. And that change makes for huge problems.....and they sit back and ignore the problem that they created.
You're literally asking people to change the rules ("most fixes are very easy"), so you can't really complain about this lol. Yeah, house rules do often mess things up - but you're apparently literally advocating for them - no, sorry, apparently demanding people house-rule RPGs to make them not be about PCs who are "super over powered", so...?
And too many players are just bad or outright jerks.
That may or may not be true, but it's certainly not relevant beyond that it's clear that some minority of people want to use bad experiences with individuals to justify claiming all players who optimize are fiends. And we can do that to any group of people, as much as it might make some people uncomfortable to realize that, and realize the parallels.