The replacement apps for iTunes are terrible and need to be addressed ASAP. They feel like early alpha versions.
I've had to use Time Machine backups, the dosdude1 tools, and multiple versions of macOS to upgrade my iTunes library properly upon moving from a 2010 iMac to a 2017 iMac. I've had to dig into folders and manually move various items. It's been a complete nightmare fixing Podcasts, Books and Audiobooks and I've lost some metadata along the way.
Only way to be a really happy Apple customer these days is to be VERY RICH.