Earlier quoted context omitted.
No, they would have stronger immune systems from repeated exposure without the extreme lockdowns NZ introduced and less hospitalizations. Respiratory viruses don't die out, they can persist in animal populations indefinitely. Sars Cov2 antibodies detected in 40% of NE deer populations for instance. Not to mention cats and dogs...
I assume you have evidence of the claim that by being regularly sick your immune system is stronger? Sure, it's run into more things it has learned to fight, but just because it knows how to fight a catalogue of things it doesn't mean that it will be better with the next novel pandemic, right?
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2841828/
We should be focusing on overall health rather than just individual infectious diseases.