If you were playing on a server you owned or for which you had ban permissions, you could do something about it. Otherwise, you had to hope that an admin was online to ban the cheater. If no one was around to take action, your option was to... sit there, take your L, and ask people to make reports (to the admins). You had the option to hop around between servers until you found one that didn't have cheaters, but is that all that different from just quitting back to matchmaking and hoping you find a match without cheaters?

Edit to add: I'm not disputing that kernel-level anticheat is bad; I agree that it is. I don't think it helps to try and hearken back to a golden age of PC gaming that didn't really exist. Maybe it was easier for server admins to manage because player populations were smaller back then, but that's about all that would have made things "better."