So I just looked into it, and apparently their intention is to turn this into a full page builder (i.e. give control over the whole page design, header, footer etc), but right now “Phase 1” just a content editor. TBH I’m a little apprehensive if they do turn it into that, because I appreciate the separation of content from the template. There are plenty of other builders out there for people who want control over everything, but I guess we’ll see how it goes.
At the moment this is a replacement for the old content editor, and with that in mind I definitely see the benefit of their block system. It’s there to structure the content while your theme still handles the overall style (which was possible in the old editor, but it kinda sucked).
Like I said, I just wish they’d give their UX/UI a serious rethink, because right now it’s a chore to select anything or move blocks around.