I've finally figured out a way to get iTunes star ratings into MC. The "import iTunes" option didn't work for me, kept getting an "invalid XML file" error. I just ended up scanning my iTunes drive via Auto Import in MC to add all the tracks contained in my iTunes library. Exporting playlists from iTunes to .M3U files and then importing to MC didn't work either, as MC ended up adding duplicate files of everything in the playlist even though they'd already been imported. Figuring out which where the 8000+ duplicates was too time consuming, so I just deleted everything and did a fresh import.
Now, the fix.
I had previously made a smart playlist in iTunes for all 5-star rated tracks. That was what I tried to export the first time. This time, I used the great Dougscripts called "Copy Rating Stars to Other Tag" script, and it embedded my 5-star ratings into the actual files for the 8000+ 5-star tracks in that playlist. The I re-ran the MC auto import to "update for external changes" and now MC sees all the 5-star ratings in the "comments" tag field. Select ALL, tag with 5-stars in MC, and done! Finally.
Two different versions depending on OS:
https://dougscripts.com/itunes/scripts/ss.php?sp=mxcopyratingstarshttps://dougscripts.com/itunes/scripts/ss.php?sp=copyratingstarsHope this helps others. Cheers!