The immunity conferred by getting COVID is quite variable from person to person, with some getting strong immunity and some getting little immunity depending on the particulars of their particular infection [1].
[1] https://www.seattletimes.com/nation-world/if-youve-already-h...
Flip the scenario, during the second wave in India, we were one of the few families in our neighborhood who were lucky that no family members caught COVID. All the local hospitals were filled, a large number of people we know survived but there were people who died around 4-5% of the people we knew who were infected and 40% who came very close to dying. The Delta variant arrived when a significant part of the elderly population had been vaccinated. You should recheck the your stats about the elderly, the second wave was brutal to under 40 folks as a good number of above 40 people had been vaccinated by the time the second wave hit.
Sure COVID might have a low fatality rate of 2-3% but 2-3% of a very huge population getting infected by a rapidly infectious disease is still a humungous number.
Or if you prefer Germany, where the most recently estimated fatality rate even for those 50 - 79 doesn't exceed 1%. It's much lower for those below this age range. https://bmcpublichealth.biomedcentral.com/articles/10.1186/s...
Many other sources back up these findings across multiple countries.
Hacker News is really filling in the COVID misinformation niche since some other sites have started acting a little bit more responsibly.