And “communal resources”? What if a private institution publishes a paper? You have a right to access that free as well? All public ally funded research is already available for free.
Publishing open access in journals maintained by the cartel is expensive. Scientists can't really afford to pay this out of pocket, so they tack it onto grant costs, reducing the money they get to actually do science. And it's overall not a pleasant experience.
These journals often offload the cost of publishing onto the authors themselves, and that money is tight. An open access publication is about the same cost as keeping an undergrad employed in my lab for a semester.
And that ignores, as others have noted, that career incentives put "Only publish in open access journals" as the kind of principled stand that might kill a new researcher's career.