Media players shouldn't be mucking with tags. I would drop such media players in a heartbeat if I found them. I typically use MPlayer locally with either MPD streaming or local files. Even if MPD gets the "feature" of retagging, all the music is on a read-only nullfs mount in its jail.
If you have "halfway" tags, I'd recommend using picard to tag your music. Most of the work is in "yeah, that looks good" before applying tags fetched from musicbrainz. If there aren't enough tags filled in, picard can fail to auto-match with the database, at which point it's a fairly manual job.
Add a "tport=8000" (at least, port 8000 is the default) query parameter to your musicbrainz URL when picard is running. It will then add links to insert release data straight into picard.