People misunderstand what federation needs to do. Email is a great model.
It’s fine to have big providers. What federation does is limit the fuckery possible. Imagine what would happen if GMail started charging $8 a month.
Having the option for competition doesn’t mean you have to use it. It’s enough that it’s possible.
It’s not. It’s an important feature. It’s not a central feature.
That’s like saying two factor authentication is a central feature of Twitter. It’s important, yes, but it’s not central.