This annoys me too. I have a work around though which may help you.
If I say Hey Siri play the ‘really cool’ playlist it will say “sorry I couldn’t find that playlist in your Apple Music” BUT if I say “Hey Siri, play one of my playlists” Siri willthen ask me which one, and if reply “really cool”it willthrn play my really cool playlist just fine.
This works as a workaround about 95% of the time.
Go figure!
I hope it helps you until this bug is fixed