I won’t deny it is widespread, and I won’t deny that you need to know it. I’ve made a decent living from being reasonably good at JavaScript/Typescript in the browser. I am one of those weirdos who can write fast JS that will work in ancient browsers still in Vanilla JS.

However, the last time I checked, a huge chunk of the web was still powered by PHP.

However, that is in the browser. You are almost always writing JavaScript, or something is getting compiled into JavaScript. 

The issue is that there are better options on the server. 

Suppose I were to choose something for a non-trivial project. I wouldn’t choose JS or PHP. e.g. I could write something in Go or C# tomorrow with good performance and the advantages of static typing.

And it’s good enough to power Netflix.

I am not fond of this argument because:

PHP still powers Facebook, last I checked. So you could make the same argument about PHP.
The needs of these large corps are not the same as you or I. Netflix can throw hundreds of programmers at a problem. A small business can’t do that. I’ve worked in big corporations that make billions, and their business-critical code was crap. They solved it by hiring many people and constantly putting out fires.