What's built in these things are quite often of 2 kinds: 1: Highlevel entity logic, something implemented by a number of game characters but nothing that reall

What's built in these things are quite often of 2 kinds: 1: Highlevel entity logic, something implemented by a number of game characters but nothing that really steals too much performance (and at that point could be rewritten). 2: Shader stuff that is often quite plain formula calculations that doesn't introduce extra iterations and most of that perf cost is just eaten up by the GPU's. But most importantly, the initial iteration isn't always the same as the final product. If something really becomes a bottleneck a developer can often rewrite the stuff in a more performant way (and often still leave parameters available for tweaking).