This was a problem for us and the lack of the ability to switch off PRs continues to cause problems.
Community submissions are virtually always throw away, particularly on a complex code base. We ended up saying it's a legal problem [1], which it partly is. But throw away not only because of quality issues, always because of project scope issues.
Yes, you feel the project is completely useless unless emoji icons animate in diagrams. That's great, fork the project and kill ours off by adding the feature (which they won't and it won't).
When you know what the project scope is, tight enforcement of that scope is critical to prevent the complexity of the project from running away and ultimately killing the project entirely.