There are two new solutions, one for Mac and one for iOS, for taking advantage of the wide array of music available on YouTube.
The first is from Coppertino as part of the iPhone version of VOX (which I’m quite fond of). As of version 1.2.0 (now on the App Store), VOX allows you to explore and stream music content on YouTube, organized by genre. You get direct access to the music, without ads. There’s a YouTube search bar and songs can be added to your own VOX playlists.
The second is from Softorino, who I’ve mentioned previously for their apps WALTR and iBetterCharge. Softorino YouTube Converter is a Mac app that will download YouTube music to your local machine, allowing offline playback without ads. If you connect an iOS device to your Mac, it can transfer the songs directly into your library.
Note that there are some potential legal issues with downloading music from YouTube. Here’s a summary and response from Softorino, I suggest reading it before grabbing any tunes.