My initial imposter syndrome came from not being able to understand enough machine language and the Apple II graphics format to be able to duplicate Ultima IV (with simultaneous sound and animation).
Not at all the same, but they did have QuickDraw II for the IIgs. This library had the benefit of using the simpler IIgs graphics modes, avoiding all the Apple II weirdness. With a little bit of searching the source can be found online.
But this exists now: https://github.com/fadden/fdraw