This is a bit of a difficult case to tackle.
Currently allmusic has errors and is missing a lot of releases, but so will other metadata providers. None of them are 100% complete or error free. @brian commented in one thread that they were in contact with their providers in order to get incorrect data fixed in a more efficient way, so roon is taking the necessary actions.
One solution would be to combine metadata from various services. Discogs has been requested several times, especially by completist that have all version of one album this is of great benefit. Combining such large databases will quickly become a behemoth of a job and even then there will be "issues". Also can recall a comment from roon (brian?) that it is not their intention to become a second allmusic, which is sensible.
That leaves the option of manually correcting, adding, editing your own metadata. To be honest I would like to do this to certain degree, but foremost I want to listen to my library and not constantly groom my metadata for whatever reason.
Would be interesting to have an open discussion on this topic.