I don't think it is the syntax that is difficult, it is the overall layout and design of a React app, and the tools that come along with it. When you start a website with regular HTML/CSS/JavaScript, you just open up index.html and start putting in HTML tags, and maybe add a .css or .js file. When you start a React app, you (usually) run create-react-app, which pulls in a million dependencies and tools you use to develop your app. Now in the long run, for a large app, those tools are useful since they make it easier to actually host your website somewhere, but the learning curve is far steeper than just opening up index.html in your web browser.
Also it is hard to determine what the best way to solve a problem in React is when there are so many different versions and additional packages people are using (ex. Redux).
React is more than JSX. I don't think the author is lazy. Some relevant points from the blog,
> I’ve done a CodeAcademy class, completed Wes Bos‘s React for Beginners course, bought books, listened to podcasts, and read tutorials. Hell, I even paid someone to build a side-project app I designed in React so I could learn how it works
> I’ve written elsewhere how I’ve never had a computer science course in my life, and I call myself a frontend designer,
> Tooling and build step stuff are tough to get my head around
Also it is hard to determine what the best way to solve a problem in React is when there are so many different versions and additional packages people are using (ex. Redux).