It's not a case of limited resources. There's twice more people on React Native team than people working on React itself, and that doesn't count all the neighbor projects that RN relies on (Metro, Yoga). And still this isn't enough.
At some point you can't "throw more people" onto the problem. Facebook can't just add a few hundred developers to the RN team and expect them to collaborate well. But that's more or less what you're asking about.
Realistically, several companies "scratching their own itches" as referred to in a sibling comment reply tends to work better because it creates focus and areas of responsibilities around real use cases.
At some point you can't "throw more people" onto the problem. Facebook can't just add a few hundred developers to the RN team and expect them to collaborate well. But that's more or less what you're asking about.
Realistically, several companies "scratching their own itches" as referred to in a sibling comment reply tends to work better because it creates focus and areas of responsibilities around real use cases.