A website like the one you describe would have some SEO benefits, since the speed is a SEO ranking factor. This example means a single HTML document with small size (some kbytes), so you would also have only one http-request, increasing the TTFB (time to first byte). This website would have an advantage over other websites; most of the CMS (WordPress, Drupal...) have a higher TTFB because they have to process the PHP before to render it in the web browser.
However, a website like this would have a bad user experience, because it wouldn't be responsive, with an ugly design, without interactivity, what also it's bad in terms of accessibility. Since the user experience is a SEO ranking factor, this would be bad for that case.
A good idea is to have a good balance between design and the resources that you include in the website. For example, here is where the static content generators win (Jekyll, Hugo, Gatsby, VuePress, Pelikan, and so on). In this cases, you generate the website before the deployment (upload it to the server). They are in essence static HTML files, so they have a fast TTFB, they don't need to process PHP (less CPU usage), so they can also handle more concurrent visitors (at the same time).
The best for SEO is the highest speed you can get while keeping a good design for the user experience. Think always with the user.