If me and my roommate are both playing against each other on a server less than 10ms away, in the normal scenario at 60fps there is still ~60ms between me clicking and it appearing on your screen - and another 60ms before I get confirmation. Now add real world conditions like “user is running YouTube in the background” or “wife opens instagram” and that latency becomes unpredictable. You still are left with the same problems. Now multiply it by 10 people who are not the same distance from the ISP and the problems multiply.