The response that I've gotten, after complaining repeatedly, is that the team simply has no time to look at any externally reported issues, and that it's essentially a waste of time opening an issue.

This makes me very sad (as an ex-FBer especially), I wish that FB would just add another 3 or 4 engineers to the team with the explicit goal of giving them the bandwidth to be good open source stewards. I'm sure the FB engineers don't like having to ignore the community, but they do as a matter of policy.