Yes, it's more complicated, and parts of it might need hacks, as there are no standard way to get subpixel layout. That's a failure of those display APIs though, not the failure of the concept of subpixel-AA itself.

> does it make correct gamma rendering more complex? switch to dark mode harder?

Most text rendering is gamma-incorrect anyway, AFAIK, subpixel-AA or not. It doesn't make it more complex, just work in a linear colorspace either way.