I think the issue (heh) is more about issues than PRs. A PR is already very concrete code and can be discussed and experimented with.
In contrast, there are a lot of issues proposing some change to Julia without sufficient discussion of motivation, alternative implementations, how it is done in other languages. This leads to long discussions going in circles.
Julia is mature enough at this point that it would be reasonable to ask that people making proposals without PRs about changing the core language in some way invest a bit of work into at least writing it up in detail.