After I become an adopter I did check with the FS to see if performing some brushing/clearing on orphaned trails was OK, and I got an 'of course it is' kind of response. It's nice to hear that others take this approach as well, but in reality the biggest thing that makes a trail suck is prolonged wet areas, and fixing that usually requires a plan (bog bridges, stepping stones, re-route, etc) that I doubt anyone is doing ad hoc. To me the best thing is for the trails to get adopted and large issues to be reported to the FS. I'm guessing that they have a gigantic list of needs, and I totally understand prioritizing more popular trails - it's about the most bang for the buck.
I'd be curious what the thoughts on people who have been hiking for 30+ years think about the relative condition of trails (are they improving, eroding, pretty much the same)?