Assuming all hours were flown at Cessna 172 cruise speed of 140mph, that gives about 2e7 * 140 = 2.8e9, divided by 332 gives about 8.4 million miles per fatality.
Compared to 85 million miles travelled per fatality on the roads in general, and about 4 million miles travelled per fatality on motorcycles.
2X better than motorcycles, 10X worse than road fatalities in general.
And that's being quite generous about the mileage.
I don't think miles travelled per fatality is a useful point of comparison for general aviation. This puts it about on par with pedestrian deaths per mile travelled, and I don't think most people would call walking "extremely dangerous."
Very similar to how dangerous motorcycle riding is. Work out approx. hours of operation from miles driven (say avg. 30-50mph) and from there use annual fatalities. [1] Given that, death-per-hour for 332 deaths/19M in flight hours is roughly comparable to the 6000 deaths seen in motorcycle accidents. Much higher than automobiles, much higher than commercial flight.
Ok, so per hour it is comparable to motorcycles. But consider also that the average private pilot only flies 100-150 hours per year.
I don't disagree that it is more dangerous than automobiles or commercial flight. But I wouldn't characterize it as "extremely dangerous." Nor would I characterize motorcycles as such.
I guess we disagree on motorcycle danger then. I consider motorcycles to be extremely dangerous (mostly to their drivers). A friend of mine died about 1.5 years ago on one. I'd had two other people (not as close) in my life die in motorcycle accidents so I used to cringe inside every time he told me he was going riding over the weekend, though I would just wish him well & to be safe. Riding made him happy, was a stress reliever for him. And as far as that goes there are probably worse habits like smoking & drinking to excess, but that doesn't make any of them non-dangerous.
Google says "motorcycles are usually ridden for around 3,000 miles per year on average" so that's less than a hundred hours. Another result says the median is 1000 and 90th percentile is around 5000.
Neither one is "extremely" dangerous but it's a far cry from "all these strict regulations make it extremely safe" like with commercial flight.
Compared to 85 million miles travelled per fatality on the roads in general, and about 4 million miles travelled per fatality on motorcycles.
2X better than motorcycles, 10X worse than road fatalities in general.
And that's being quite generous about the mileage.