> The distros could add new APIs could be added to expose new capabilities.
Those exist already. With Debian, Alpine, Fedora,... you can put anything on top of the kernel in the userland. Android goes with a restricted version.
It's the same with MacOS. It's Unix, but with proprietary add-ons and systems. And lately, with more restrictions.
How does those existing make Android not a good platform? I don't fully understand the point you are trying to make.
By restrictions do you mean having proper capability based security instead of letting all apps have access to everything? These restrictions are a good thing.
Limited userland and limited access to it. Sandboxing may be good, but the user may need some software that needs to escape it. Fedora Silverblue is a promising direction, but interacting with the base system is currently a pain.
Those exist already. With Debian, Alpine, Fedora,... you can put anything on top of the kernel in the userland. Android goes with a restricted version.
It's the same with MacOS. It's Unix, but with proprietary add-ons and systems. And lately, with more restrictions.