Perhaps a more charitable interpretation of the article is that when writing a larger application in React you'll be led from React-the-library (which is "just JavaScript") into React-the-ecosystem, which looks less like "just JavaScript" and more like the other frameworks.
You can definitely write your application in React without external dependencies, but how is a beginner expected to do that, especially with all these other popular libraries around?
I think the more salient point here is that React-the-ecosystem is just the JavaScript ecosystem. There were very few packages mentioned that are strictly only useful with React.
Besides the issues with building stadiums in states without a football tradition, Brazil is facing the problem that people just don't go to the stadium much. For example, the national league, which finished its third round last week, has had only 3 games with more than 20000 spectators so far.
That was already a big problem before the World Cup, and only became bigger after it since the cost of maintaining the stadiums is much higher now, and so are ticket prices.
You can definitely write your application in React without external dependencies, but how is a beginner expected to do that, especially with all these other popular libraries around?