Although I can and have managed domains and mail services, I don’t agree that what you described is for the majority. Do you really think that’s true?
The biggest impediment is probably that most people aren’t willing to pay (say) $10 per month for a domain and email hosting like they do for streaming services, because they’re used to email being free. So they remain at the mercy of the big providers.
But I can at least encourage the HN crowd here to move to independent services and to use their own domain.