God dammit we've had standards that work. Apple and Google are responsible for killing all of the decent messaging protocols by censoring the clients from their app stores.
When smartphones came out people modified IRC with support for push brokers and message replay but because of app stores this means push brokers for community maintained clients have to be maintained by the individual volunteer paying (yes! paying, shut up about the free dev accounts they don't allow you to send push notifications) for the "privilege" of submitting the app (meaning they have low to zero availability.) The relay Mozilla maintains allows servers and users to choose who brokers push messages but Apple and Google screw over their users for profit and this is the result.
This is a stretch for Android at least, Google charges a one-time $25 fee for a Play Store developer account and provides unlimited push notifications for no extra charge.
When smartphones came out people modified IRC with support for push brokers and message replay but because of app stores this means push brokers for community maintained clients have to be maintained by the individual volunteer paying (yes! paying, shut up about the free dev accounts they don't allow you to send push notifications) for the "privilege" of submitting the app (meaning they have low to zero availability.) The relay Mozilla maintains allows servers and users to choose who brokers push messages but Apple and Google screw over their users for profit and this is the result.
Smartphone app stores have made IM unusable.