"Herd immunity from natural exposure is dangerous and isn't going to happen. A year and a half on, only 4% of the population here has tested positive."
That's because a lot of people have had it, never felt too bad, and never got tested while the virus was actively replicating in their body. This has been proven in randomized serological tests in many jurisdictions now.
That would show up in test positivity rates, and it has not. At least not here. The only time when test positivity rate deviated significantly from daily counts was in the first wave spring 2020 when testing infrastructure wasn't there yet.
I can't say anything about places in the US where it spread like crazy through the population in the first wave. But I've seen no studies to back up what you're saying here in Canada. Also various cities have been doing testing of sewer water for the virus, and the values have matched, roughly (and in advance), what has been seen in testing rates.
That's because a lot of people have had it, never felt too bad, and never got tested while the virus was actively replicating in their body. This has been proven in randomized serological tests in many jurisdictions now.