[diggan]

> How does the domination of a few big game engines(unity/unreal) change this? I get the impression that they handle more and more of the actual compute intensive stuff, and 'nobody' writes their own engines anymore?

You still have to know what you're doing. Cities: Skylines 2 is a good example, as the first installation had awful performance when playing bigger cities, and it wasn't very good at parallelizing that work.

For the second game, they seem to have gone all in with Unity ECS, which changes your entire architecture (especially if you use it wholesale like developers of Cities: Skylines did), which is something you have to explicitly do. Now the second game is a lot better at using all available cores, but it does introduce a lot of complexity compared to the approach they took in the first game.