Your "question" is wrong on several points. No virus stops with herd immunity. They are slowed by herd immunity. By definition, members of the herd can still get the disease, and even spread it to other members of the herd, but there are no major outbreaks possible. So even if we had herd immunity, it would not mean that the virus would not be dangerous.
Covid-19's problem is not that herd immunity does not work, but that herd immunity is not sustainable. Covid-19 immunity, especially natural immunity, fades quickly, which makes getting herd immunity very difficult.
There are a whole bunch of viruses that can cause the common cold, but not "SARS type" viruses. The most common cause is a rhinovirus, which is a totally different group of viruses from Covid-19. A less common cause are coronaviruses, which would be related to Covid-19. Also influenza viruses cause colds, which are very treatable with vaccines.
Basically, you are wrong on every level.
Masks and quarantining have worked against colds.
Antivirals have never been as effective as vaccines, and they certainly do kill people. They are brutal.
Without herd immunity stopping it from spreading, it will continue to spread over and over again. You start by saying there is no end to the deaths, remember?