This is only true for a certain class of games that rely on multiplayer. Many games are singleplayer where the meat exists on the game engine. There's two sub sections of this as well. Real time and non-real time.
Realtime means streaming updates from all users. Games like fortnight or pubg are like this. Non-realtime means like checkers or multiplayer chess. If you are doing the later rather then the former I would say you're still in traditional web development where shit is still relatively easy because an HTTP server is good enough.
The former is what is really hard, and that kind of thing is what I would refer to as backend game development. If you are doing that, then likely you're not a traditional web developer anymore.