How hard is it to nullify a publisher's copyright claim (which has been consented by the authors), based on the fact that they do none of the work, thus indirectly appropriating public money?
It's not possible in the US. If the authors validly transferred copyright, they validly transferred copyright. (There is a takeback provision after 50 years or so, but ...)
Schools and academics can drop subscriptions or boycott submissions. Law can be changed.
Even if that's future-looking only, it can change the balance of interests for journal publishers.