I do not know if there are any real developers here to share their point of view, so I will. I am full-stack developer, experienced in PHP, Javascript, CSS, WordPress API, React and of course Gutenberg, although I did work with other page builders. I create custom themes and plugins. Gutenberg gives me capability to prepare easy admin part, with blocks tailored to customers needs. In the end, developed solution is much easier for customer (not so much options as in page builders), adapted to their level of requirements and of course, much faster than with other page builders as described here. I also found custom tweaking (I mean changing code – Javascript, PHP, CSS) with page builders more cumbersome than with Gutenberg. I think Gutenberg really excells for customer who hires experienced developer.