There are "weight classes" in boxing and MMA / why not on Chess.com?!?

Is this really fair, letting heavy weights beat up strawweight fighters? REcently, players with more than double the ratings have appeared in tournaments. Surprise! The bad players get outclassed.

TBH, is this intentional? Can't the better players compete with their own competitors?

There are class and rating restricted events and in bigger events, rating or class restricted sections, so that already exists. There are also Opens sections where anyone can play. For smaller events, there may only be an Open section, since they don't pull enough players to do that.

Even when I was still doing live games, I tended to avoid tournaments. They were simply places where my hopes would get crushed.