It's funny how, for years, we've been trying to get away from HTML mixed with code (specially in spaguetti PHP), just to get back to something similar again.
It's not the same thing. JSX is a user experience enhancement for developers.
PHP templates advertise, and do in fact provides, most of the same benefits as JSX. There are almost no new concepts to learn, the syntax is the same as the language proper, and developers have the full expressive power of that language at their disposal wherever they want it.
In practice, however, this seems to fail more often than not in a couple of ways. First, inexperienced developers (i.e. all developers at some point in their career) have a hard time resisting the urge to inline their business logic into their presentation logic. And second, the resulting templates are as often as not illegible, often requiring a reader to trace substantial chunks of tangentially related procedural logic in order to understand what will actually be rendered.
It's important to remember that PHP templates seemed like a good idea at the time. They did, and do, have real short-term benefits, and talented developers can leverage those benefits to great effect. But it turns out those benefits come with real long-term penalties, and besides, many developers are too green or too pressed for time or just don't care enough about the task at hand to wield that power consistently well enough to reliably reap the benefits in the first place. The PHP community has spent the last decade painfully crawling out of that tar pit; I'm not thrilled to see the JS community happily diving into it.