It still feels like the majority of CSS/JS should be controlled from theme part and not from a plugin. Backend should be more involved in block generation the majority of blocks should only control the data, not the actual CSS/HTML/JS code.

Simplest example:

- Plugin/theme "A" wants to display image gallery as elements
- Plugin/theme "B" wants to display image gallery as elements

Gutenberg block generated gallery with elements. What should plugin/theme "B" do? Parse HTML (ew)? Write the second image gallery block?