Herd immunity is a myth. A lie. The Lancet recently published an article explaining it is, essentially, an impossibility. We have no idea if it would even work, and to reach the levels where we could even find out if it does, the suffering and loss would have to be many times what we have seen already.
To control behavior, we need coherent messaging (which we totally lack) and overwhelming social pressure to force responsible behavior. And we also need to take away the option to do stupid things as far as possible, so risky places like bars, theatres, and theme parks need to be closed. Now.