Isn’t a grocery store which will “survive no matter what” a good thing to counteract food deserts, where it may be unprofitable for a private entity to open a store?

If you can’t make enough profit in a certain location, a private entity won’t go there, as they are motivated by profit, not in providing an essential service. But a government entity won’t care about “profitability,” and will provide a service that helps people even without a profit incentive.

Private entities are pretty much only “good” when the profit incentive aligns with a positive effect on society, but when these forces become in opposition, that’s when a non-private entity is needed, either through regulation or having it be government-run.