While a lamentable situation, this has been addressed to a considerable degree and it's not all that bad. For example Matrix has its Push Gateway API (https://matrix.org/docs/spec/push_gateway/r0.1.1#id4) which allows any client to register any kind of push service. This means that any given iOS app, for example, can maintain its own backend for feeding events into APNs like Apple requires. I'm not as familiar with it but I believe XEP-0357 does something similar.