Last I used Kodi, it was a great app for, like, DIY entertainment management but utterly useless if you are expecting to use something like Spotify or YouTube.

It has been a while though, so I might be outdated on this, but I'm guessing it's still not possible to log into spotify from it, browse the spotify library / your playlists, use device remote play from your phone to the tv, and so on. Same goes for youtube (though I do remember some useful-ish youtube plugins, they didn't go beyond logged-out browsing)

Logged in YouTube works fine. I use both (android and Kodi) and honestly it's not so much worse on Kodi. Plus you don't need to sideload apks to disable the current ad flood

If you have Kodi on Android, you can have "links" (I don't remember the name in Kodi, sorry) for the Spotify, Youtube, Netflix, etc Android apps within Kodi.

Pretty sure Spotify works fine. They have a fully functioning API for premium users. Netflix might be a problem though.

Aren't most of those add-ons depending on real-debrid now, meaning a $5/month subscription? Why not Netflix then?

No? Not the Kodi I have at least, it feels like a huge open source community with many clunky but usually working apps.