Changing from PHP wouldn't change WordPress, it's general engineering approach hasn't changed since it gained popularity a decade or more ago.
Except for Gutenberg, which could be characterized as an admin facing HTML editor powered by React components but with an interfacing layer between Gutenberg and React, so only some of your React knowledge applies. It gets saved as HTML. The actual served content is still served as PHP generated HTML. React isn't involved in the client workflow.
All of this javascript code is of course bootstrapped and defined by PHP hooks including dependencies, and redefined again in the JS, so you're constantly diving between PHP and JS just to set up the JS.
Now to work on WordPress idiomatically you need a whole new set of skills that introduce a whole new slew of problems. So it's not best practice or well engineered PHP, and it's not best practice or idiomatic React. The docs for Gutenberg are incomplete, so no luck there either.
Another platform that failed in this same way was Magento 2. They want to use the Cool Kids Tooling, but they want to do it their way, so there's all this Bullshit™ inbetween and you get a hamfisted barely documented Frankenstein's monster. The third party tooling docs can't help you because of the proprietary integration making much of it no longer apply, and all the novel domain knowledge to get it to work is floating around in Stackoverflow threads and github issue tickets.
Except for Gutenberg, which could be characterized as an admin facing HTML editor powered by React components but with an interfacing layer between Gutenberg and React, so only some of your React knowledge applies. It gets saved as HTML. The actual served content is still served as PHP generated HTML. React isn't involved in the client workflow.
All of this javascript code is of course bootstrapped and defined by PHP hooks including dependencies, and redefined again in the JS, so you're constantly diving between PHP and JS just to set up the JS.
Now to work on WordPress idiomatically you need a whole new set of skills that introduce a whole new slew of problems. So it's not best practice or well engineered PHP, and it's not best practice or idiomatic React. The docs for Gutenberg are incomplete, so no luck there either.
Another platform that failed in this same way was Magento 2. They want to use the Cool Kids Tooling, but they want to do it their way, so there's all this Bullshit™ inbetween and you get a hamfisted barely documented Frankenstein's monster. The third party tooling docs can't help you because of the proprietary integration making much of it no longer apply, and all the novel domain knowledge to get it to work is floating around in Stackoverflow threads and github issue tickets.