An alternative to journals would be to switch to the arXiv model everywhere: let anyone publish with a bare minimum of moderation, make papers explicitly versioned, and let peer review happen out in the open. Already for decades, the importance of a paper has been measured by citations, not publication in a prestigious journal.
No thanks. I have no interest in peer reviewing anything for free if it's going to be handed over to closed source AI companies. And before some facile comment about Elsevier comes along, no I don't review for them either and it's clearly not the same.
I think you still run into the problem that writers will vastly outnumber readers, so that risks turning the project into a write-only dumping ground. From there you have the same old discovery issues, where traditionally scientists relied on reputation as a first stage filter.
How do you build reputation in that environment?