I am at present cleaning up my library so that I can restart fresh removing unnecessary metadata.
So you want to start 100% fresh with no files in your library at all right?
But somehow, after I removed all my folders from file/library/import/Config Auto-import, I still see all my album arts in my MC 21.
The auto import settings do not affect what is in the library "right now". When you remove folders from auto import, it tells MC to stop checking in those folders for new files. It does not remove any existing files from the library.
The fastest, easiest way to clear (clean) the library is to use the clear function: File > Library > Clear Library .
That will remove all files and start you from scratch again. Note that any changes you made to metadata (album, artist, etc) that are saved in the media files themselves (MP3s, FLACs, etc) will still be there when you re-import the files, as that data is inside the files themselves.
Good luck.
Brian.