I am very concerned about the direction of Gutenberg. In my opinion this "Post Edit Screen" replacement is way out of scope of replacing TinyMCE editor.

The scope creep on the project has been raised numerous times, and to my knowledge, has not been addressed in detail. See the github ticket regarding metaboxes for details.

If we could get a complete answer as to why Gutenberg needs to be a full screen replacement, and why metaboxes are considered "legacy" maybe we would better understand the philosophy behind this.

I feel some of us are seeing the editor developers wanting to build something new and cool, ( which is great ), but maybe got a little bit carried away working with the fun stuff and replacing everything. I also think there is a bit of not invented here syndrome. Every time I hear "legacy metaboxes" I basically hear, that was invented a while ago by others so it's old and no good. You need to get on board with the cool kids and re-do everything in the latest ( current ) fad, React.

How many years will it take before we start to consider React, the new editor and blocks "legacy" and "not invented here". I guess probably not long, backbone.js and the 3 year old completely redone media library is probably starting to loose it's cool factor.