I've been playing CoD since the very first game and the MP religiously up from Modern Warfare (2007) to Black Ops 3 and I can tell you that people accuse practically every one of being a hacker or cheater. I could probably start up Modern Warfare (2019) right now and play a dozen matches and probably get a handful of cheater/hacker accusations.
Anyway, cheating has always been a thing in CoD (and probably most FPS games). Activision/Infinity Ward won't be able to catch them all. At least they included the ability to disable cross-play as I'm sure if there is a high amount of cheaters in the game, most of them are coming from the PC side of things.