This change to the editor is part of a trend with WordPress of moving away from the dedicated purpose of blogging, towards satisfying the more general-purpose needs of a full-featured CMS. Typically blogs feature a unified design for posts, so that in the process of writing individual posts, you can focus more on the content than on the layout and organization of the piece. Time will tell whether block-based editing ends up being common in blogging contexts.
Sigh. A harsh reality. WordPress needs to make money. Blogging at the amateur level doesn’t make them any money.
Matt is himself, a blogger. I hope he’ll have the guts to fork WordPress to the open source community so we who have built our entire online life on WordPress can continue using it with security patches and improvements that support web browsers 20 years from now.