I would like to share my experiences and test with GP and Gutenberg. I think that above all Themes and Gutenberg will have a future, while pagebuilders have to dress warmly.
I like to use Gutenberg very much because I just have to use the editor directly and have an enormous flexibility to design my contribution. The danger? The design is not uniform. I would like to give an example: I use the newest block from Gberg (http://prntscr.com/laf66u) but this creates an imbalance to other blocks (no fixed padding to the headline and no uniform font to the headlines). In comparison the example of the button: http://prntscr.com/laf76o (padding: 11px 24px;)
What I mean is: I would like to have a theme that allows me to define a uniform design in one place without having to screw in a hundred places.
I know that GP and Gberg are in their infancy, but maybe you can include that in the roadmap.
And as always: additional blocks (Accordion, Alert or even a Table of Contents block would be very fancy.)
I (and i think others too) would be very happy about that.
Note that it isn’t even a beta yet and you’ll want to clear your browser cache if you install it.
As for the issue, it looks like the block styling inside Gutenberg is the issue? GP itself can’t add CSS for every block without bloating the theme. In some cases, Gutenberg itself needs to make sure the default styles for their blocks is good.