I didn’t check all missing songs (wsy to many), but the ones I did check were actually missing, and it wasn’t just an import or transfer error. I mostly checked those that were important to me and stood out in the import-list marked as missing when quickly scanning across them.

I have probably 100+ playlists. Not having folders is just not feasible. I wish use playlists in non-normal ways, more like notes in some cases, which is harder or impossible without folders. So for me it isn’t an option to use a service that doesn’t have them.