I'm not convinced it blows up. It might also end up placing a larger burden on contributors, and especially first-time contributors, to provide concise, high-quality documentation that justifies their contribution.
I'm thinking of something like: Explain, in at most 300 characters, why we should merge your change, or at least why we should invest the time to read a longer explanation (somethings things ARE complex). If you don't do that, or those 300 characters aren't convincing, or have nothing to do with your change or the longer explanation, then you get a canned response so the maintainers waste minimal time.
I'm thinking of something like: Explain, in at most 300 characters, why we should merge your change, or at least why we should invest the time to read a longer explanation (somethings things ARE complex). If you don't do that, or those 300 characters aren't convincing, or have nothing to do with your change or the longer explanation, then you get a canned response so the maintainers waste minimal time.