Having a blueprint parent theme and/or a standardized frontend framework would be a good idea. At least in theory.

The problem I believe is where we are at right now.

From a theme-developing standpoint - now with Gutenberg - we're in this weird state where (at least some) blocks don't provide the necessary customization options so the theme must apply its own default styling for the blocks to not feel out of place.

Integrating with G is not easy either with the CSS class inconsistencies, etc.

It's this back and forth that every. single. theme. would have to go through because there's no standard.

In general, Guternberg is not an isolated design system like page builders are and kind of blends in with the theme.

If we'd be able to style all the aspects of the block in Gutenberg - great.
If Gutenberg blocks came with no styling at all and the theme would take care of things - great (well, not great and unrealistic - but in theory it would at least make sense).

Currently, we're right inbetween which leads to a lot of inconsitencies.