This post spends quite a bit talking about beginners who are learning Javascript, React, and JSX all at once. Of course they aren't going to get it right immediately, if they didn't get tripped up on JSX they'd get tripped up on something else. "Beginners don't get it" might be the weakest argument I've heard so far.
Pick languages/frameworks that will produce easily maintainable code and will survive naturally after your departure from a company. New developers have a learning curve no matter what. The steeper you make that curve, the more danger you put your codebase in and the more likely you are to set them up to fail.
But since when have we been any good at identifying future needs or identifying maintainable code? Just be consistent, try to at least leave SOME documentation for the next guy, and don't be actively malicious.
"React is, in my opinion, the premier way to build big, fast Web apps with JavaScript."
Nowhere in the documentation does it stress that it's easy to learn or ideal for beginners. If you don't know Javascript, writing React applications (or any application, really) is going to be painful. Full stop. JSX adds cognitive load when writing code, but reduces cognitive load when comparing the DOM to the component that created it. Given the amount of time I spent debugging and refactoring, I'm happy to use JSX.
Maybe it's the article's title that has understandably rankled some people by seemingly maligning JSX. However, I think it's a very valid concern to have when ramping up a team that's unfamiliar with JS and React.
I'm not in the situation of ramping up a team unfamiliar as the author was. But it sounds like he was experienced with JS and React himself. Or are you suggesting he should replace his team with people more familiar with JS+React?
Note that the author isn't suggesting a return to separate template pages. He is suggesting a system for creating React elements that uses simple functions and JavaScript syntax rather than the custom syntax of JSX.
Medium has become the analog to Tumblr posts for opinionated engineers to whine about things that don't really impact development in ways that matter.
Really all this developer had to do was talk about Hyperscript in a positive way and I would have found this post interesting instead of rolling my eyes paragraph after paragraph. Oh poor you and your angle brackets, such a burden! Putting HTML directly into my JavaScript is awesome and I never want to go back to separate template files ever again. It's wonderful and results in great code that works well, is readable, and is easy to test.