Trying out the new app right now as I love listening to classical while working, however it has some major flaws.
You can, of course, AirPlay to a speaker, specifically a HomePod speaker, however you can't "control" what's playing on it.
For example, with Apple Music, I can "Control Other Speakers & TVs", and directly control what's played on them. This then allows me to leave the house or use my phone for other purposes. Maybe have a call, what a video, whatever...but with Apple Music Classical, only AirPlay is available (like Spotify), so the moment I do something else on my phone, the music stops, or for example, when I use my Apple TV where I have my HomePods paired, the music stops.
I hope they resolve this soon. Otherwise, it's rather nice!