This new UI change is definitely unwelcome. I have the original Apple watch, and I never synced playlists directly to my watch, since its cumbersome, and I always have my iPhone with me.
I much preferred to use the Apple Watch as a remote to select and play music through my Airpods withouts having to take my iPhone out of my pocket. I can no longer view my entire library on my iPhone.
This honestly sucked a lot during my flights this past weekend when I was hoping to have a fluid experience with my iPhone in my pocket, my watch on my wrist, and my airpods on.