It seems like even Android being "open" these days is an incomplete story, as it's almost more like a barebones Linux kernel build with some bare UI and libraries now, rather than a mobile OS distribution with standard apps that vendors can build on.
You seemingly have to do everything yourself, which begs the question why not just go full blown Linux distribution, and throw on some sort of Android app emulation?
I largely agree, especially when focused on consumer devices. Professionally I'm building a product built on top of AOSP, and it's been really nice to have a standard target and all the tooling that Android brings. It could be better but the base AOSP does have a lot of value as a general purpose OS.
I'm in the midst of debating moving us to just Linux or sticking with Android, and the list of things to replace isn't insignificant.
You seemingly have to do everything yourself, which begs the question why not just go full blown Linux distribution, and throw on some sort of Android app emulation?