Songs missing from Apple Music library

I have a MacBook Pro (15-inch, mid 2015) that I recently upgraded to MacOS Monterey. That also means that I went from using the iTunes app to the Apple Music app. Yes, I know I'm way behind the times! Anyway, in order to free up enough space on my computer for the OS updates, I moved some big media file libraries (music, movies, and photos) to an external hard drive and am trying to reopen everything. Movies look all good, photos are slowly syncing, but music isn't quite right. I can see the original files (sorted by artist and album) in the "iTunes Music" subfolder of the copied "iTunes" folder. But when I opened the "iTunes Library.itl" file, it's only showing about 1,090 songs. I'd guess that's less than 10% of the full library. Apple Music is also missing all of my old playlists. For the music that is showing in Apple Music - some were purchased through iTunes, some were downloaded from other websites, some were ripped from the physical media. There doesn't seem to be any consistency in what's visible vs what's missing. Is the annoying solution just uploading it all into Apple Music again, or am I missing something??

Original files in Finder:

Many of those artists missing from Apple Music: