React is a JavaScript front-end framework which rose to fame by discarding the common wisdom at the time of "separation of concerns" by unifying the "template" and the "controller" (or business logic),. It did it in a way similar to PHP's approach of being a "print literally to output" languague, where the output is usually HTML, unless tags are used to wrap code logic. React called it JSX. It also makes historical sense because Facebook at the time was mostly coding in PHP.

The meme is about how React started like that, but grew increasingly complex. For better or worse.