"You are INCREDIBLY uncalibrated with the real world."
I don't think I am. My estimate that >50% may have been a bit generous, but I think I'm in the ballpark. The perspective of the majority of visitors on this site is skewed due to the fact that many here are long-distance runners. Most (not all) individuals who gravitate towards long-distance running have below-average sprint speed and struggle mightily to break 60 in the quarter, so they believe erroneously that the average person must lack the ability to break 60. Furthermore, how many people actually do 6 months worth of 400m-specific training? Very few! So how can you say most people couldn't do it with proper training? What evidence do you base this on? Do you host a 400m training camp we don't know about? Have you tried and failed to coach a multitude of young men to sub-60 quarters?
Will I concede that the majority of young males lack sub-60 ability in their CURRENT state of fitness. Absolutely! I used to be a sub-50 guy in college, but even sub-60 would be out of my reach at this point (I'm 32 years old). I'm quite out of shape, like most American males. But give me a month or two to prep, and I got it. Give the average young adult male another 4-5 months of prep and they're knockin' on 60 as well.
I think back to my high school track team. We were not a very good track team (usually ranked 4th or 5th in our 8-team conference). We didn't have try outs. Any one who wanted to join the team was on the team. And we had a pretty large team (about 40 guys). Of those ~40 dudes, about 12 so so ran the 400m, either regularly or occasionally. In the open 400 or as part of a relay. I don't recall a single one of those dozen guys failing to break 60, at least once or twice. Again, I emphasize the fact that this was not a team comprised of cream of the crop sprinters who passed some kind of try out to join the varsity team. This was just some random guys who wanted to do the sprint events. A couple of us had exceptional speed and ran down in the realm of 50-52. A few were in the 54-56 range. And a few were in the 57-59 range. I do recall there were a couple of long-distance guys who insisted they could not break 60, but again, these are guys who did not do sprint-specific training and didn't do much lifting either. I repeat, of all the guys on my high school team who trained with the sprinters and attempted the 400m, all of them broke 60.