Publishing sits within an ecosystem of science funding that is in most of the Western world dominated by government. Until that system is disrupted, it's going to be hard to break up publishing monopolies...

Academics (who unfortunately are the only people anymore who do anything that can be described as "science" anymore) apply for government grants based on their published impact factors. These reputations for "top tier" journals like Science and Nature allow them to act like a cartel that controls access to this resource, which is in turn monetized by the academics.

However, unless the incentives (RE funding structure) for science is changed, scientists couldn't just start putting stuff on Nostr, as cool of an idea as that is. They need to show their "impact factors" on their grant reports, and there's no impact factor here.