Very good points.
My suspicion is that Covid may be more like the common cold coronaviruses than we think:
*first infection is severe, except in kids where it is just a cold
*reinfection occurs every few years, but those later ones are mild.
The only difference with Covid is that it is new, so most of us never got that first infection in childhood.
The challenge with the common cold is that it’s actually caused by any one of over 200 different viruses from several different families. Most are actually caused by a rhinovirus. There are four viruses in the coronavirus family known to caused colds in humans. What we call the “common cold” is really just a collection of symptoms shared by infections with any of those over 200 different viruses.
It does seem that immunity from that first bout is holding up even when new variants arise, so that’s really good news. Hopefully that continues to be the case and this thing goes away the way SARS2003 and MERS2012 both did.