Even if our immune system memory doesn't last very long for these types of viruses, wouldn't young people getting exposed to it now likely reduce its impact long term?
It also seems like >95% of people who die from this are over 55 years old. When you get into your 70s~80s, aren't common colds one of the things that result in natural deaths, due to an aging immune system allowing pneumonia to set in where it wouldn't in a younger person?