I was able to do that back in 1990 on FidoNet, again on usuenet in the mid-late 90s, on IRC in the 90s and 00s and using google to search forums in the 00's until the centralized systems killed them. IRC, usenet and others still run, I can still email people I want to talk to as well.
What you are arguing for is a smooth, slick, paid for, UX. Minimal UI's and typing "@" in names is too much. Looking at lists is annoying so you want it curated for you. VCs dumped money on private UX and now people think its essential. We have always been able to communicate directly, there is no technical limitation.
Its in the minds of the users and the unwillingness of some to see a different domain name or try a new UX flow.
Get some VC money drop 20m or so on Fedi UX and all of a sudden people will see very little difference.
Or just wait, I remember when the linux desktop was a joke too.