I honestly don't understand why JSTOR, Elsevier and others like them still need to exist. Top universities should just found a non-profit, per subject, with a single paid facilitator and a single paid editor (per journal) to find peer reviewers and edit the papers into a monthly journal. Modern tech has made it ridiculously easy to type, edit and publish such a thing if the inputs are LaTeX, Word, Markdown files or a…
A 100% open and free journal cannot achieve selectivity without having some judgement and bias applied. One that's hard for an intrepid band of volunteers to recreate without funding and full time commitment. Who will be the editors? There's also the problem of how to create a new journal that has the prestige of an old established one. Which new journal will we select to have the prestige?
But yes, they have become parasites, who prey on the free labor of eager young academics, take their work and sell access to it, enforce copyrights on knowledge created by taxpayer money, and bundle useless journals in with important ones so everyone has to pay more.
It's in the public interest for academic fields and the universities to come up with a reasonable alternative.