I agree with your perspective, it does come across like someone who has had success learning one stack and that's great, but it's hardly a picture of the varied landscape. There's nothing wrong with PHP and I've seen plenty of businesses do just great with it. I've also seen companies doing equivalent with Ruby, and Go, etc, and even a mix of languages. You can do all this without falling into the pitfalls (which can happy in any language/ecosystem).
There's nothing wrong with choosing PHP, and also nothing wrong with other alternatives too.