Some of the best co-op I ever played was in Rainbow Six 3, but I played with 7 players, and I don’t remember if it will let you mix and match humans with bots on your squad. You’ll need a gaming VPN to play co-op, also, since the servers are gone.

Halo is always a good time, as is Gears of War, and it kind of sucks that outside of Borderlands, these are the most recent recommendations I can come up with, but this genre has been left to rot in live service hell.