What’s going to happen, if this ever goes through, is that the networks will open some kind of api so outsiders can send and be sent basic messages. And you will never be happy using it because you’ll always look like an outsider.
And there is no way to fix this because a big draw of these networks is that they keep adding new features and they are not in the old api so you can’t use them.
And of course it’s going to be a big source of spam so users will get the ability to block the outside from sending messages to them, which means you can’t reach half the people you want.