"However, it is a far cry from what a good theme designer can do with the flexibility of plain ol’ CSS."

Surely the ability to enqueue shared editor CSS and register custom styles for blocks with unique classnames (.is-style-x) gives frontend developers all the same freedom they would have with bespoke menus?
I already make heavy use of the block styles system to apply custom CSS to specific blocks without interfering with any existing styles, and the idea of doing so in conjunction with basic controls like background colours and text colour really excites me.