A large problem is that the companies with the money to address the issue will only do so starting from a position of a walled-garden rather than a system like email that in principle is open to anyone's mua/mailserver?

We have a proliferation of communication apps that don't talk to each other because each of the capitalistic driving forces wants to kill every other app so there's wins (even if there app is much worse than competitors).

This is where you need cooperation for progress and where capitalism, with greed as the driving force, utterly fails.