Most Wordpress sites are not operated by programmers, they are run by non technical people who just want a wysiwyg editor and a save button. While static site builders ask you to write markdown files, compile the result, upload it to a server, and if you want to collaborate you have to add git to that.
There almost needs to be an admin app which presents a Wordpress admin like ui but has no public exposure, and then it compiles the site to dump on s3 for the production. But as far as I’m aware no one has built this.
It is kind of surprising that no one tried to do an updated version.
You're describing the Jamstack or headless CMS concept verbatim.
I fixed so many sites back in the day by people who thought they knew what they were doing.