In reply to Leonardo Losoviz.

Actually, Gutenberg can save content to post meta in addition to the post content field: https://developer.wordpress.org/block-editor/tutorials/metabox/meta-block-1-intro/

Here's an example of "sticky" Gutenberg fields which could be used to replace meta boxes: https://riad.blog/2017/12/11/with-gutenberg-what-happens-to-my-custom-fields/