I think the major concerns to me are:
1) The number of other diseases, especially cancer, going undiagnosed over several month, as well as people who have dying of things for not seeking medical attention
2) The number of kids at risk students who will simply never graduate being out of formal school for the better part of 12-18 months. Not graduating high school results in negative outcomes in pretty much every category including life expectancy. I'm thinking primarily of those that are 14-17 now. The privileged among us (which is most on this board), our kids will get through with their own laptop, and their own bedrooms and offices, and parents looking over their shoulder. But this is going to devastate communities that and further inequality in a way that could reverberate for a generation.
Both of these things can be mitigated by a modified opening policy which most of us are in now. I think most people are seeing their doctors and getting treatment, etc. You don't have to be 100% open like nothing is happening to reduce the impact of these consequences. But I think you have to trade some expansion of the virus in exchange for better outcomes in these areas.
But to me, the idea of a 100% lockdown going on for 8-12 months is a total non-starter because of these reasons.