Imagine coordinating not just one or two people to do the exact same thing but 328 million people. That alone is a huge obstacle in a free society. If we all did it at the same time, we could do it in two weeks. Very unrealistic. So that is why the leeway. The virus itself has an incubation of about two-weeks hence why the initial idea was 15 days and even then that was only to prevent hospitals from being overwhelmed. At the time, we didn't really know how effective this virus would be. There was a possibility that the heat might've been enough to see it weaken or die off on it's own. Medical experts also warned also not to rely on that even though it was a possibility, yet we did, and here we are.
The difference between experts and the non-experts is that the experts record and observe and record data objectively and give the best response to what information they have. When that information changes, then it is necessary to change tactics. What is happening is that instead of relying on experts, people are quick to accuse them of not knowing what they're doing, but not because they made mistakes despite being cautious but because people don't like what they're hearing as advice.
Herd immunity takes years, if not decades, to have an effective outcome on a new virus. And not all virus are susceptible such as the AIDS and HIV virus. In fact, Covid-19 specifically targets the immune system but because it's a coronavirus and not a rhinovirus it's actually weaker in most respects unless the infected person has an underlying medical condition that could be made worse by the presence of Covid-19.
While I agree the changes our society will have to go through to adapt to this crisis are not practical in regards to the average American's daily routine; doing absolutely nothing is not practical either. A compromise would be for people to practice social distancing, maintain personal hygiene, wear masks, and not openly be dicks to other people in public. That last one is really hard for most Americans.
