[lukifer]

Not OP, but I'll give my answer. The unification of different media types in iTunes is a feature, not a bug. (I clung to Retroactive as long as I could; I forget what made me cry uncle.) For actual music, Music.app has been okay, bugs notwithstanding. (I don't use Apple Music, only my local library.)

But the other apps simply aren't as full-featured as iTunes; they align more with Apple's interests as an appliance maker and content vendor (original iTunes preceded the iTunes Store by several years). TV.app preserves some power-user features, like Smart Playlists, while stripping out basics like "Show In Finder". But the one that really grinds my gears is the way audiobooks have been shoe-horned into Books.app, with any semblance of user sovereignty removed.

Example: few years ago, I was planning a road trip, and wanted to quickly filter down a shortlist of audiobooks: "Unread, Genre: Science Fiction, Length < 12 hrs". Not only does the UI offer no affordances for that: it doesn't even display audiobook length, let alone allow sorting by it! I had to dig to find where the files are stored (in `~/Library/Containers`, with gibberish file names), then write a Bash script to `ffprobe` the files and parse the results. When audiobooks were managed by iTunes, this would have been trivial.