The current issue with ALL of the stem splitters is that they are using a subtractive model. When they split out the tracks.... the ones that come out the best are the ones with no competition in that part of the sonic landscape. These tend to be the vocals, bass, and drums, although not always. Even the drums and bass tend to come out sounding a bit "fuzzy" or "mushy" as opposed to solid tracks, but slightly less so than things like the guitars and pianos.

Until they are able to rebuild a solid track, as opposed to cobbling the bits together of the extracted track, you really won't have a good quality stem splitter.

It's for this reason, the subtractive issue, that I actually prefer to replace the extracted tracks with either BB tracks or my own recorded instruments.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.