This is anecdotal evidence and trying to derive patterns from it is dangerous. We know that COVID-19 is much more dangerous than the typical annual flu and we are at risk of overrunning the icus.
Their final paragraph goes beyond just sharing an anecdote and into making prescriptive judgements about how society should approach the virus based on those anecdotes in contravention of the medical consensus. I presume that's the issue people have with it.