Just a data point: Google scholar regularly reminds me of any publications of mine that list US gov funding that do not have a publicly accessible PDF.

You are already allowed to (at least in tech) provide a preprint and public PDF on personal (non commercial) or educational web sites.

And Google scholar does associate those with the publishers links, as an alternative source.

So, it's not like we couldn't provide all R&D for free already. At least in tech.