Such situations where the servers were flooded with cheaters existed for decades and it still exists just like on any multiplayer game. Server owners are ultimately the responsible ones when's coming about preventing malicious players.
If you ever see a cheater in the server, do not hesitate to contact the server owner or server's moderator/s to enforce a permanent ban so they're unable to join again. Otherwise, use the advantage of the Kick system of CS2D if you see other players around so many people can vote a kick request on the cheater.
If none of them satisfies you, then your last chance is to leave the server and go to another. Saying "cheaters are everywhere" is kinda vague as you imply that every single server is invaded by mass cheaters which is not always the case. By the way, posting threads about cheaters / hackers is not allowed according to FAQ/RULES - PLEASE READ!. Such threads do contain important and useful information as they're pinned (marked as important) for a reason and you should never ignore them.