How to unrate multiple album ratings at the same time?

I was looking to do the same thing the OP requested here. This was my solution:

Open the Music app (formerly iTunes in macOS 10.14 and earlier) and do one of the following:

• create a new smart playlist with the criteria that album rating does not equal zero stars (the star to the left of the first star) then open up that smart playlist and select all the songs therein
• sort tracks by album rating and select all the songs that have a non-zero album rating.

Next, open up Script Editor.app and paste in the following script:

tell application "Music"
    repeat with theSong in selection
        set album rating of theSong to 0
    end repeat
end tell

You may need to run it more than once as it may fail as the selection changes while songs are being removed from the smart playlist. After a successful execution, all manual album ratings will be removed. Some albums may still have grayed out ratings: these are from the song ratings themselves and aren't actually album ratings.

I was also having trouble with getting rid of the normal Rating hollow stars, as opposed to the Album Rating stars (which I didn't even know they existed). What finally worked for me was to show the Album Rating as an option on the column, then manually delete them off the ones that were showing on the Rating column as hollow stars, and it worked!, I just picked any rated song from that given album and it took away all of them in that album. Hopefully this makes some sense.

There is currently a defect in iTunes which is causing some albums to attain USER ratings (black stars) instead of ESTIMATED ratings (grey stars). When this happens, it causes the album's individual tracks to have ESTIMATED ratings (grey stars), which messes up your smart playlists.