Every time I use the Improver on any of my plalists, it loops between 'Upgrade Quality' and 'Match to Library'. It suggests 282 sound quality improvements, so I do those, then it suggests Matching the same 282 tracks to the library, so I do that. Then it reverts back to suggesting 282 sound quality improvements for the same tracks.
Describe your network setup
500+ meg internet connection from Spectrum, TPLink Wifi6 router, Roon server runs on a Windows 10 PC (i7, 16GB RAM, 1TB SSD).
After you upgrade quality, you can either keep the upgrades (from Tidal and Qobuz) or you can lose the upgrades and revert to tracks in your Roon library. Your other option is to click on the individual suggested upgrades, then click three dots on the right and go to Roon Versions. There you can see what your options are and add the better albums to your Roon library if you want. Then cycle through the playlist improver again.
EDIT: The Roon Playlist Improver is somewhat of an iterative process. Run through it a few times until you narrow down to a smaller number of suggested improvements and an equal number of library matches. Then, if you want to, go through the process of adding the improvements to your Roon library.