This is a very valid question. It points at a substantial problem of the musicbrainz data: The high number of low quality entries, lacking info allowing us to identify the exact release (often dating back to some freedb entry) or even having contradicting info. I have to say that discogs is better in this respect.
I agree: If all the thin info of a low-info MB release matches yours, just hijack it and make something consistent out of it. Otherwise, setting the release quality to low is always a good idea. In the past I even merged such low-info releases into better ones if everything was consistent. It should be a long term goal to improve as many of those low-info releases as possible.
The disappointing thing about the “release data qualtity” feature right now is that it is well hidden. I think we should put a lot more emphasis on rating and displaying release data quality as I wrote there. If you agree, please consider voting for this ticket!