Seamless (gapless) playback (that actually works). Equalizer. Cross-fade. Volume normalization. Buttons that react when you click them, not 5 seconds later. Desktop app, I'll even take a shitty electron wrapper. Literally anything related to customization of the application/playback/UI/music library.

If I'm setting the bar too high, just playing audio without freezing or bugging out constantly would already be a huge improvement.

> there is no successor, so unlikely in the near future

What is Google's successor to Google+, Stadia, Reader, Wave, Buzz, Domains, blocklist feature, YouTube Streams, Inbox, Health, Answers?...