Is this what happens with Call of Duty? My observation is I would play very good for a couple of days, often 1st or 2nd player in the 12 people group. Then, next few days I am placed with a bunched of assumed cheaters (seemingly seeing thru wall, headshot but not dead, jump slide then shoot mid air with a gamepad...).

Activision CoD uses EOMM, engagement optimized match making. They’re optimizing for your to stay on, much like a gambler playing slots. You allow one win where the player is matched with lesser opponents, and then the next X games, you’re the lesser opponent.

It’s all tuned to keep you playing and want that dopamine hit of a win that’s always just around the corner.

If you're doing so well that you're saying CoD starts treating you as a cheater, then what's probably happening is you're playing people below your skill level until the matchmaker adjusts.

Then once the game puts you with people closer to your skill level, the best of them feel like they're cheating (and to be clear, some definitely are, but to the people you were stomping you also probably seemed similarly clairvoyant with impossible aim and movement)

Skill based matchmaking is controversial, but the truth is more games have been killed by an infinite loop of skilled players stomping new players so badly that the new players never become skilled players, than the opposite.