iOS 15.5 is available now in the beta version and brings back a deleted function

Apple has just confirmed that with their new system version iOS 15.5 all users will be able to change the playback rate for subscription content from Apple Music in third-party applications.

The feature was removed in the previous update, probably, because of some bugs that prevented the app from working correctly.

You need to remeber however that iOS 15.5 is in beta stage so if you aren't part of the beta programm, you need to wait a bit longer for the update.