Push notifications are a tricky one because they only really work when there's one central distribution point, for performance/battery/etc. Apple does it this way too, and almost every mobile platform does the same thing. Yes you can sit in the background and hold a connection open or poll on some platforms, but it's not a good experience.

I see a thriving third-party ecosystem around push notifications as a marketing channel. Yes the low level APIs end up going via the central platform, but they are remarkably low level, and the business value comes from the automation, easier integration, tracking, rich notifications, etc. Companies like Urban Airship have been around for well over a decade doing this.

Are these central platforms holding you back? If so I'm interested to know what you're unable to do that you would be able to do better.

(This is all my own opinion, mostly from developing for iOS in a previous role, not that of my employer where I'm nothing to do with push)