You don't follow games recently (meaning 10 years at least). There are few publishers that put pretty nasty DRM protections inside that run constantly, take few % of the CPU and do constant full memory checks (among other things). Performance drop is visible unless you have obscurely expensive hardware.

This is kind of expected for online gaming due to many folks fucked up mentality of using cheats and playing with rest of the crowd (some psychologists could probably go quite deep on breaking this down to mostly childhood issues). If you play on your own, its just a pain in the a.

Many people buy the game and then play pirated version, just to avoid this kind of punishment of the lawful citizens.