Comment by luke5441

I think the biggest problem is that the main way to use it is as a HTTP response handler, whereas other languages are more general purpose. So when a developer wants to develop themselves outside of a HTTP response handler, they need to switch languages.

Of couse it can be argued that PHP can be used outside this one way as well, but even e.g. https://symfony.com/doc/current/mercure.html is using golang.