Facebook definitely takes a platform approach with Oculus. The Oculus Quest is a great device at a great price. It has done the most to make VR a mainstream accessible thing. And yet because of Facebook's behavior and what we know about Facebook as a company in general, we really, really must not let it become the dominant system. Hopefully, other companies will improve their user experiences to match (because Oculus certainly doesn't have a hardware advantage, everyone is pretty much running the exact, same hardware profile with only minor differences).
TBH, this thing happens. look at gog vs steam vs <shall not be named>; this strategy doesn't always pay off though, consider the Nintendo console lineup (curated, small but higher quality) compared to Sony PlayStation - in the end Sony won that one, and my own belief is the reason that less curation led to some indie (not developed by Sony) gems.
And you're still stuck using Oculus' APIs. There are no open source APIs for accessing the device sensor data or rendering. Regular Android apps (minus Google Play Services) can run on the devices as tiny windows, and then you can get some super-hacky input as touch events on the app view, but it's really not usable. I think it even forces software rendering, because I've seen some really bad performance out of it (I found out about it after not having an app configured incorrectly before uploading it on my own for my own development). It's basically there as a fallback for Android's default Settings view, which you use to configure the developer settings like enabling USB debugging.
