Legality and ethics are often disjoint, and for many people Sci-Hub is pretty clearly a case where piracy is the ethical thing to do.
My personal opinion is this: tax dollars pay for a huge proportion of the research that is then reviewed by volunteers (whose pay also comes out of taxes) and then published in journals that charge insane prices to host a PDF of this taxpayer-funded research. Sci-Hub takes this publicly-funded research and makes it available to the public like it always should have been.
At least in the US, all government-funded research will be required to be freely available immediately starting in 2026. It's unclear what the overall impact will be. Certainly this access is a good thing, but it's unclear how publishers will respond.
It's possible authors might be forced to pay publishing fees for open access, which would then inflate grant budgets (since this only applies to government research, this means the taxpayer is footing the bill). They may choose to be open access by default, in which case, another source of revenue will be necessary. Part of the challenge is that for many academics, it's necessary for advancement to publish in prestigious venues which are not always open access.
I can't figure out why in 2023 running a journal costs very much money at all. The authors are paid by someone else, the peer reviewers are paid by someone else, and an online-only journal would be completely acceptable today. What other overhead do these publications have?
Limiting to online-only journals (which is already the case with many journals), there's still editors, administrative staff, and hosting costs. I'm sure many would argue (and I would agree) that this shouldn't require exorbitant sums of money.
However, some money is still required and I'm not sure where this would come from aside from funds collected from either authors or consumers (institutional or otherwise). I'm not saying the model we have is the only possible model, just that I don't think there's an obvious alternative that solves all the various aspects of the problem.
My personal opinion is this: tax dollars pay for a huge proportion of the research that is then reviewed by volunteers (whose pay also comes out of taxes) and then published in journals that charge insane prices to host a PDF of this taxpayer-funded research. Sci-Hub takes this publicly-funded research and makes it available to the public like it always should have been.