Well, if you compare our stats with the ones from TheAudioDB, we still have 300.000 more releases with cover art than they have releases/“albums” in all. And keep in mind that one of the things TheAudioDB wants to do, is to provide access to album and artist images…
I don’t think the ratio necessarily is as important as the fact that we do continue to get more releases with cover art. As long as we have more correct cover art for more releases than elsewhere, I don’t care if that means 1% of releases or 91%. 
(I’d also personally rather have 1 release added with full ARs than 1 release added with cover art (and no ARs), but that’s just me.)