Many guns have 50-100 round mags in the AR class. It's the M4's basic lack of recoil + 60 round mags that make it THE weapon. People who can't control recoil don't need to and can literally aim at a person and hold down fire. It's especially helpful for aim assist people on console, because though you may not be getting headshots as easily, it's going to give you plenty of center mass shots.
Guns like the AK and the FAL should be monsters for good players, but they're not. They're dogshit. They just translate completely differently in game than on paper. The FAL is supposed to be the best gun for anyone with good aim, but the recoil on it and the fire rate combined are just awful. The AK can get huge mags as well (80?), but the recoil and slow fire rate again just kill it. M4 is fast, 60 rounds give you a lot of miss leeway, and hits harder than some of the other ARs, all while having no recoil if properly kitted.
It's like the R99/Wingman in Apex. At a certain point if you were running anything except maybe a peacekeeper, you weren't sweaty enough. R99 was just fastest TTK with no aim required, insta killing full targets without even using your brain. The Wingman was what the FAL SHOULD be and was hugely rewarding to people who can aim and hit headshots, but the Wingman also hit really fucking hard for body shots so it didn't have much of a downside until the eventual nerfs.
M4's, Vehicles, and Heartbeat Sensors need a tune up. Probably a removal for heartbeat honestly, as it makes Ghost a necessary perk eliminating any other Perk 2s (overkill, restock, etc). Kind of bullshit. Thermals could probably be removed too, honestly, but slot 1 perks aren't as important so Cold-Blooded isn't too awful, but again, like 80% of the people are running it.
In solos if you want to win you run Cold-Blooded/Ghost/X with an M4 with a 60 round mag and a heartbeat sensor. Why make a class system with options when you end up having to play the same bullshit as everyone else? This is the kind of balance that games like Realm Royale died because of. Variety BR's are amazing ideas, but without constant data monitoring of class/skill/weapon usage and actual good feedback (NOT FUCKING REDDIT) you'll just stagnate your game with one meta or you'll ruin everything at once by over-tuning.
And all of this is said before anything about cheaters. That's it's own beast and they're not doing great. 70,000 banned people? Cool. Those are probably something like 10,000 actual people just making new free accounts. And they'll just keep doing it until their auto cheat detection works.