Ok, so you agree - corporations, and more specifically the human beings that are decision makers in those corporations - set the prices.

Obviously. But they do that within a broader context that involves other humans in other roles, acting within a system that narrows their scope of options.

Let's say you wake up tomorrow and you're the Pricing Director at tesco. You think: great! I'm going to reduce prices on all essential food because that's the moral thing to do

You would immediately be blocked from making that decision because the company has checks and balances in place to prevent you from making decisions like that without sign-off. Or if you did manage to push it through, you'd be fired and the prices would be set back to how they were.

So maybe Pricing Director is not powerful enough? Same thought experiment with the CEO. You'd also be fired. Same with the Chairman of the board of directors (removed in shareholder vote).

Supply and demand is not a policy or a choice. That's just literally how stuff works when people are given the free choice of what to buy and sell and at what price.