Toilet troubleshooting

I have a toilet, 20+ years old.

For far too long I have put up with it clogging or not flushing completely. Liquid or solid flush doesn't matter. The main problem is the flush will swirl and stay the same level.

I'll snake it and plunge it and it will be fine for a few days, maybe weeks then back to the headaches. Never tries to overflow. Some of the under rim jets don't work anymore, if they ever did.

Hoping it's just a re-install, or put in a new one type (which I'm fine with) problem. But I fear bigger issue lurking just because I have that stupid kind of mental wiring always wondering if it's a bigger problem.

I'm just looking for some experienced points of view on this.