It doesn't have built-in websocket support so it can F off. Build better dev tools and feel bad. Even the plugin that used to be usable isn't supported on the new FF.
Yes, the FF Dev-Tools need some love. They have some cool features which are unavailable in Chrome (e.g. the CSS Grid view), but overall they tend to be less accessible (managing (wifi/usb) connected devices and service workers should be much easier and more reliable).