If we all made a reasonable effort to isolate, even if not perfect, then it seems to me that the virus would be forced to evolve to spread more easily with fewe

If we all made a reasonable effort to isolate, even if not perfect, then it seems to me that the virus would be forced to evolve to spread more easily with fewer symptoms which is what we want. How well did "herd immunity" work in WWI, where they sent the sick to the crowded hospitals?