But what if we want to customise everything?

Imagine meticulously customising your window manager and compositor to get rid of bloat like animations and effects only to have some google dev decide to draw their own and break your webbrowser in the process -.-

I don’t get it. Why each application would want to draw their own shadow independently of any other? It is obvious to me that no such thing should be done by the app, but the window manager or compositor should be doing this. Otherwise we will end up with a mess, duplication of code, each window different shadow?