As long as Gutenberg doesn't offer the functionality of the best pagebuilders today, webdesigners WILL keep using Elementor, DIVI, ... in combination with Gutenberg. (= per definition a hybrid system). So therefore Gutenberg will cause even more fragmentation, because the future of Wordpress will be hybrid for a long time to come.

And at the same time, more and more theme builders will begin creating their OWN Gutenberg blocks, mimicking pagebuilder functionality and hereby again ... creating even more fragmentation.

Gutenberg still has a long way to go and therefore it won't be able to solve the fragmentation in this fragmented pagebuilder- and bloated “multipurpose” theme-world, which was actually created by ... Wordpress itself. Because Wordpress is unable to close the gap between what WordPress core does and what users want.

Like Android ONE can't solve Android's fragmentation, Gutenberg won't solve WordPress' fragmentation. There are just to many parties involved, each going their own way.