1. We are already working towards herd immunity. The social distancing is to slow the spread of the disease throughout the population, not to stop it from spreading. Had we not done the social distancing and shutdown, we would have reached herd immunity much faster at the cost of completely overwhelming our health care system (which still happened in the hot zones that popped up before the shutdown). This would increase deaths from COVID-19, as well as every other source of emergency (car crashes, gunshots, workplace accidents... etc wouldn't get cared for in an overwhelmed heathcare system. The amount of deaths would be staggering. We will not safely reach herd immunity without a vaccine according to every expert I've read discuss this (I'm open to any sources you can provide that suggest otherwise).
2. You mention the bubonic plague, as if that is a highly contagious pathogen that passes from person to person. The bubonic plague is rarely spread from person to person. Social distancing or shutting down portions of the economy wouldn't stop the bubonic plague. You are comparing apples to cucumbers.
3. We haven't had a pandemic on this level in 100 years, but you think we are going to have another one like this every decade for the foreseeable future? I mean it is possible I suppose, but I'd love to know what you are basing this on. We have had diseases that have a higher mortality rate by far, but they were no where near as contagious as COVID-19 (SARS 15% death rate). We've had diseases that spread as easy or easier than COVID-19 but they were not as deadly (H1N1 infected 24% of the world, but only killed .02% of those infected.) The fact that COVID-19 can lie dormant for so long before symptoms present, the fact that it takes long term care for those who present severe symptoms and the fact that it is so contagious make this a rare pandemic. When was the last time American hospitals were running out of space to store dead bodies during a pandemic? The answer to that question should let you know this isn't a once in every ten years type of event.