> Also, this looks like a bleak picture for the JAMStack if Wordpress keeps growing no?

The JAMStack has a usability problem. That's why wordpress keeps growing. What do i need for wordpress? some cheap(maybe even free) webspace and a database. updates to the wordpress core are quite simple doable via webinterface. done. with this even the biggest simpleton can write blogposts.

with a jam stack? headless cmses, blogposts written in markdown, config in "frontmatter", building and deploying your blog, versioning via git, not even a litte autocomplete. even i recommend wordpress because i have not the time and nerves to teach non-it people to use the JAMStack.