@nprofile1q... It's easy to say that one doesn't need better protocols after those better protocols have become so ubiquitous that you don't even realize how you're using them yourself.
Apple APNS and Google FCM use
#XMPP technology to deliver push messages instantly. All the other messengers listed (
#Signal,
#Element,
#DeltaChat) thus use XMPP technology. Everyone uses XMPP, but when it is about marketing, suddenly XMPP is not necessary.