But publication and aggregation no longer need to be performed together. That was a limitation of print publishing, since the cost of publication was high enough that you really needed to do your aggregation/filtering first.

Now the act of publishing is trivially cheap, so you can simply let everyone publish everything first, and apply aggregation and filtering second.

If you took all the attendees of those two conferences and gave them a collaborative website for rating and reviewing papers, you'd probably get something just as good as the old journals, and probably faster.