The herd immunity concept is an interesting one and may very well work in certain parts of the world, but you’re spot on that the US isn’t one of those places. Trying to accelerate the spread to the younger/healthier portion of the population, while isolating the at risk community, can create herd immunity and stop the spread as there aren’t enough uninfected bodies for the virus to continue spreading at an exponential rate.
The issue for the US is most experts state you need a 60% infection rate to achieve herd immunity and our population has a +60% at risk pool, possibly higher when you factor in those who care for a parent or grandparent, thus indirectly moving them and their entire family in the at risk profile. We simply couldn’t get to the 60% without exposing a significant portion of those at risk.
Totally agree on half-measures, there’s absolutely no evidence that these partial precautions will have a material impact on the spread, it’s got to be all or nothing.