Yes, everything old is new again. I just browsed the docs, but it seems it's not so different, other than it's automatically run on servers all over the world. Temporarily, this is for free. Also, it automatically updates after pushing a commit to GitHub, which seems nice.
It's written in js/React so you can share frontend and backend code and write the entire site in one language or even using the exact same components for server side and client side rendering. This is a boon for development. Ignore the nay-sayers.
Not a web developer. How is this different from CGI or a regular web server? This an honest question - I don't understand the significance.