In reply to George Stephanis.

$george, it seems like you have kind of weird definition of CMS. In your definition a CMS is something that includes an editor and then all the possible kitchen sinks in the world.
Why would a CMS need a rest api, oembed server, react etc.

Actually even as CMS wordpress is not a very good one, images made public right when uploaded? No way to edit a published post and check the impact on the site without actually publishing the changes, no revision control for widget, and post meta, no user permission checks for shortcodes…

WordPress puts the bar very low when it comes to have a CMS that is at about the same level of it.