A few years ago, there used to be community reviewers of pull requests to the AWS provider - indeed I reviewed dozens after leaving HashiCorp. My own access for this got removed in (IIRC) late 2018, and I’d assume this was across the board.
I don’t think it’s conceivable that any reasonable number of employees could satisfy the demand of maintaining the first-party provider set in the current form, without leveraging the community. However, I for one will not sign a CLA that allows proprietary relicensing, and I’d guess most people who could give meaningful reviews are in a similar boat, or already work on the provider teams.
However, I’m also not sure that there is a “priority problem” as such - most providers don’t make HashiCorp money from consumers or contributors, and employee time is better spent on products which contribute to a positive bottom line.
The Terraform Provider Registry has made it much more palatable to run a fork of any given provider than it was previously - I’d recommend doing so if you have functionality you need that hasn’t been integrated.