This is a really great article.
You also can't build apps that use decentralized backends that receive notifications on that platform. All notifications have to come from the centralized app developer.
Sharecropping is beginning to be the only way.
I understand this is not possible for specific apps that need smartphone notifications to function properly, but when you think about it: a lot of (web)apps don't need that.
In general, one might need less notifications than one thinks.