In summary, SEO means that a specific post is going to have in the header, paragraph titles and paragraph bodies some words and many more, and these words are in demand.
So, if the site does not have default SEO functionality (Joomla, WordPress 6 Block), and if is fast or slow, these are not make the site better in SEO.
The problem is when the site has SEO and is slow.
Speed is good but also SEO is needed (build in or by actions of advanced users).
