I agree the quality is not great. When I use it, I often convert stems (they have a really good stem splitter on their site) to midi using melodyne. It works pretty well but sometimes there are random sounds on the stem that you have to scrub, either in melodyne or in the midi track.
Unfortunately, I can’t split drums effectively on Melodyne. Drums have been my Achilles heel in my music production forever. I’ve always used BIAB drums but they’re far from ideal.
The Suno drum tracks are very good except any cymbals other than hats. Crash and ride cymbals end up sounding like hiss in a mix.