That is indeed true. But, I remember the time when we were rolling out nginx back in 2000's and exactly the same thing was said about Apache.

Not if the people switching is the cool crowd. Which is exactly what I think is happening here

HAProxy is pretty popular too.

Because most nginx usage is different?

Of course, you can serve static assets using Envoy, and maybe even connect a fascgi app without very much hassle. But it's quite a bit less straightforward.