I think the new heart icon next to any song in any playlist is a not neccessary change. There are many people who don't like the new design of the heart icon being literally next to every song. It feels like an icon that should only be there if the song is actually a song you really like. It is confusing and not as visually appealing as previous icons/options.
My suggestion: Instead of having the icon being permanently displayed, only make it visible if you hover your mouse cursor over it. This way people can still easily add songs to their favorite songs while there are no more heart icons "everywhere".