I, and a lot of other people really dislikes the choise to remove the Star-button. The reasons are many, "Your music" doesn't have the functions I used in Star, and other people used it in many different ways. But there's an extremly easy way to fix this:
Make an option where you can choose if you want the Star- or the Save-button!
This is such an obvious choise, that I can't understand why you havent already implemented it. My first reaction when I found out that the Star-button was removed, was to go looking for this option. In my head it was obvious that when you remove a feature/system, you make it optional to bring it back. You could have done the same with the look, and avoided people from being angry with your new look. I'm not to fond of that either, but that I can live with.
If you are smart, you can even let it be a multiple choise option; where you can choose if you want a Star-button, Save-button, neither or both.
Updated on 2018-06-16
A similar idea has already been suggested here:
It has been discussed within the Spotify Team in charge and it has sadly been decided that this idea will not be implemented any time soon. However, Spotify will revisit those idea topics from time to time, so hopefully it will be implemented in the future. ;)