Blocks are movable. Writers often want to move paragraph when editing article. Moving element is a lot easier and precise.
Actually, writers often want to move a chunk when editing, and this is exponentially more difficult in Gutenberg than in the current editor.
A chunk is not necessarily a paragraph. It is a passage of any length or content, defined by the writer for any given chunk. So I might have one chunk with three paragraphs; another with four and an image; another with two and two images, etc. In the current editor I can move such chunks with a simple copy-and-paste.
Now try moving such a chunk with Gutenberg. Clue: you can’t. Instead, you have to move stuff paragraph by paragraph (and also move each image separately because each image has its own block). That’s a nightmare.
Even apart from all Gutenberg’s other shortcomings — and there are many — this alone makes it hopeless for writing anything but a short blog post.