Does wix/WordPress have the application level UX capabilities of VueJS/react before becoming a plugin writer? I find the comparison grossly disingenuous. If you were asked to write a TodoMVC in VueJS/react vs WordPress, you'd probably figure out how to start (and/or have already finished a proof of concept) in an hour with VueJS. In WordPress, you'd be 6 hours into the introduction to WordPress plugins and still unsure if a TodoMVC is possible or if WP is the right tool. If you legitimately think what people do with VueJS can be done just as well by juniors in WordPress, then you don't understand what VueJS/react actually do.
Or Wix or Wordpress even.
But for someone who has taken the trouble to develop an in-depth knowledge of, and facility with, the underlying technologies (HTML, CSS and JS), front end development is not that difficult or mysterious. And for them, these frameworks make the process needlessly complex rather than simpler.