The point of conferences is discussing ideas, which asynchronously is hard to say the least. Remote conferencing is already a big step down compared to in person conferences. Doing them asynchronously I fear that would put the last nail on the coffin.
It wouldn't be exactly like an old-school conference, but I feel like it would have it's place as a medium for exchanging ideas.
My thing is an irc/slack-like chat system, that allows you to leave both text and audio messages (which get auto-transcribed) in the same chat channel, so you can have asynchronous audio conversations blended with traditional async text chats.
As a play on async, it's called heysync[1]. It isn't ready for people to use yet, and it's also made more for 'work communication', as opposed to conferences, but it's very neat to see different takes on asynchronous communications coming up over time.
I think to blame tech for the problem with connectedness is only one part of the problem.