I think Casey hit the nail on the head here. We used to have hardware with standardized ABIs, some of which had extensions (like Tandy graphics compared to CGA). That made it relatively trivial to make OSs, which is what PC booter games did really. DOS itself barely abstracted anything at all, because you didn't need drivers for standardized hardware ABIs.

Unfortunately the only way to deal with that is to give up on the idea of running on a majority of existing PC hardware and target only a small subset of commodity hardware. Ideally it would all be open, to ensure it isn't going anywhere for a while, but sadly there is no such system.

I'm glad to see I'm not the only one who thinks Users and Groups are the wrong abstraction for systems like this.