Couldn't care less about the library, any managing whatsoever, album covers, tags, lyrics etc.
LOL you're using a music library whether you think you are or not.
Indeed. Jennepen, I started out like you, I just wanted a player for selected files or playlists. Then I found that even though I had no visible library per se, everything I played was still being written and appended into the MusicBeeLibrary.mbl file. So I still had a "library", but no way to view it or use the endless tools/management/sorting that MusicBee provides with it. Deleted the whole thing and started over with a declared library, and never looked back. I hope you know that the "library" isn't some folder where all your files get moved to, or extra copies thereof. Your files stay exactly where they always were (unless you have manually activated the "auto-organize" option, I recommend you NOT do that). The library is just a file containing references to your music files location and other info on how to arrange/play them within the MusicBee view, etc.
That said, if you insist on not having to deal with a library at all, useable or otherwise, players like Foobar and AIMP will allow you to do that, but of course at the trade-off of the zillion features MusicBee has to offer.