Yeah, we are, but pretty inefficiently. All the complexity in real-time multiplayer comes from trying to pretend everyone is in lockstep, while not actually synchronizing them 60+ times per second.

This makes it an open-ended problem - many of the tricks work under very specific assumptions (e.g. low latency, trustworthy clients), and fail when those assumptions no longer hold (e.g. people notice stutter, cheaters cheat). The job is to find the right set of tricks for your use case. And it starts with knowing the tricks in the first place (or inventing new ones), as it's pretty much a specialization of its own.