So, a funny (or should I say, surprising) thing happened... I got a new 16" MacBook Pro, so I had no choice but to start using the Music app. I took a chance and decided to just dive in to see what would happen. So, I did the following:
I opened the Music app in Catalina on my new MacBook Pro, turned off or unchecked Sync Library, Automatic Downloads, Always check for available downloads, Automatically update artwork, then disabled 'Apple Music' (because I do not use it, nor do I store any of my music in iCloud).
I closed the Music app in Catalina, copied my current iTunes folder (as is from the 'Music' folder in Mojave) to the 'Music' folder in Catalina.
I opened the Music app again in Catalina, while holding down the option key, then selected the 'iTunes Library.itl', which is my original and legacy iTunes library still sitting in the iTunes folder, which is now in the Music folder on my new MacBook Pro running Catalina.
The Music app launched, and much to my surprise (based on all the horror stories I've read), all my playlists were intact (hundreds of them), in the correct song order, and there were no broken song links, and all the artwork (that I took hours and hours to apply myself) within each playlist started to pop up. It took about 20-30 minutes total for all playlists to populate the proper artwork (and it didn't come from Apple's servers). No running for days, no high CPU usage, even though the Music app sometimes shows 'updating album artwork', when really, it's not.
Now, mind you, I have a large (500GB) music library, and I only work within the structured playlists that I create (which would cover about half of the files in my library, so far). So, any music files that fall outside of my playlists are uncategorized and have either been downloaded, ripped from CDs or purchased through iTunes. Until these songs are used in future playlists, the song/album artwork and song naming schemes haven't been updated yet (if needed), so I am very much play-list only based and focused. Be it long sequenced playlists that shift genres that define several eras throughout each year, or artist anthologies and so on, all the chosen music has been curated in playlists with updated and complete artwork to my liking, and all of this retained in the Music app in Catalina. I wanted to mention this, as my use-case may be different from others.
My starred and 'loved' items also retained, as well as each song's play-count. What didn't retain is the column order while in 'song view' mode, but that's easily fixable (while still a major PITA).
So while I am very happy that all my playlists, artwork, play-counts, star ratings and so on copied over exactly as is, I now see why the Music app is hated by most. It makes iTunes feel like the best music app that ever existed. The functionality that they took away in the Music app is pointless and actually makes the app worse than iTunes ever was. The lack of logic and flow is staggering. The horrible new search function that populates albums instead of songs/files, and the fact that you can no longer search within a playlist is totally backwards and makes no sense. Our music libraries are databases, and they should function as such. Apple's obsession with album views (their way or no way) is getting out of hand.
The fact that you can no longer hit the back and forward buttons endlessly to navigate to all previous screens regardless where you landed (library, store, playlists) is mind boggling (and that single back button looks ridiculous sitting there, alone, floating). And so on and so on. They even removed the time played so far, and the time remaining while a song is playing, you have to actually MOUSE OVER that area to see how long a song has left. WTF?! Why?
Whoever thought that REMOVING useful features and functionality from iTunes (to make it appear as if they've re-written a lighter and faster Music app) should not be allowed to develop at Apple. When are they going to learn that LESS options/buttons/choices is actually more difficult for the average user? By all means don't make it look like a hot mess with a million options a la Microsoft, but there is a happy medium, and the last version of iTunes is a good example of that.
So, while the Music app will get me by, now that all of my playlists are copied over and intact, if given the chance, I'd go back to iTunes in a heartbeat. Now that Apple is pushing Apple Music (streaming), I doubt that they are going to put all the features from iTunes back into the Music app any time soon. They are obsessed with bland interfaces and no options and limited features, because somehow, that's 'easier' to your average user.
The bottom line is, if it were possible to downgrade to Mojave on the 16" MacBook Pro, I would, simply to use iTunes again. The new Music app makes navigating and creating playlists unnecessarily difficult and cumbersome. I wish they would've just stripped the TV and PodCast functionality out of iTunes, and carried it over to Catalina as is.
So, do we think the Music app will ever be as functional and usable as iTunes, or, is this it?