What happened vs. what would have happened is a factor here. They said hospitals will become over-run, and they would have (and sounds like some were in NYC area) ..... BUT, that doesn't mean they would have everywhere. Some of this was a factor of learning what level of hospitalization would be required - and that was originally over-estimated. That was an error. But the other hand is that the mitigation measures appear to have turned this around, and so it's hard to take current numbers and say hey you were wrong when you said to shut down. (But it does make a great case that it is past time to start opening up these areas)
As for the did we need to shut down everywhere - I think that message was never explored in full, at least not in the public discourse that the policy makers were willing to have. It was shut it all down. I think that is because the concern was if you let more rural areas remain going that it would cause the cities to just ignore it ..... or maybe it was just short-sighted. I do think we saw some of this in Texas though. The state kept looser restrictions over all but areas like Houston laid a decent hammer down and all the suburbs generally followed suit.