Video games can scale just fine with many cores, including MMOs and games like Minecraft. Veloren, for example, uses multiple cores everywhere for just about everything--most of the gameplay loop, physics, chunk meshing, world generation, realtime simulation, rendering (can be parallelized a lot further now that we've switched to wgpu), networking, and background tasks like snapshotting persistence--and it is certainly not hard to find places where parallelization yields real speedup (quite the opposite--every time we further parallelize physics it yields significant performance improvements!). There are many hard problems in video game performance, but "games just can't make good use of multiple cores" is not one of them.

If anything, I often wish we could rely on many more cores being available than actually are! It is certainly far far easier to see real performance wins with multicore than by using multiple servers, which introduce very heavy coordination costs.