I agree with your rant for the most part. OCs built explicitly to be OP tend to be terrible as characters and have bad writing in a story-telling sense. Though, I'd argue most OCs in general are total garbage.

"Edgy teen drug abuser" does not really make much of a better character when written by a novice than "Muh invincibility shields have invincibility on top of their invincibility." Both are terrible.

However, your title is extremely click-baity and seems to be steeped in personal bias. You dislike hax, and that's fine, but it doesn't seem to be based on anything objective other than "sometimes they're written poorly."

Some of the most nuanced characters I've ever read are also some of the most powerful in all of fiction. They wield hax abilities like multiverse erasure, reality reset, god creation, etc. And still they make for amazing characters.

Maybe it's easier to write a weaker character well, but being powerful does not make personality go away. it doesn't make shortcomings go away either. That's just your personal bias speaking. Maybe Superman or Batman or whatever comic book hero you think is OP or too hax is a bad character. Great. Doesn't hold much bearing on the vast array of other "OP" or "hax" characters that are actually good.