I wasn't trying to argue people have some sort of natural or genetic intelligence that far exceeds people of a few centuries or millennia ago. Genetic evolution doesn't happen that quickly. The point was we have progressed in terms of studying, publishing and understanding certain natural processes and phenomena relative to a couple hundred years ago. Look at the medical fields. A few centuries ago we didn't even understand infection, and had actual doctors believing blood-letting was therapeutic.
There is no "artificial age group." The skills and trades of centuries ago are what are increasingly useless, and information is not useless, we just have a lot more advanced specialization and there are a lot of areas where the information goes unused because a different specialization is pursued.
That's quite a positive spin on the way children were treated in centuries past. Children were much more regularly beaten (not spanked to be corrected in the moment of doing something very bad, but literally beaten) with the belief that they would only succeed if taught via corporal punishment. This wasn't actually an honest attempt at teaching youth, it was psychologically troubled adults taking their warped emotions out on children. Traditional social conservatives routinely spin it differently by just contrasting it with the overly sheltering snowflake attitudes you find in some places today. Just because some people are ridiculous little snowflakes doesn't mean the way children were physically abused centuries ago was "a good thing." It's also disingenuous to claim child labor was an honest attempt at teaching skills and trades. It very often was not educational, it was just straight up labor. Grueling, repetitive labor.
In ancient Greece, by law parents could abandon newborns in the woods to die of exposure. If strangers adopted them, they made them into slaves. Pederasty (child rape) was normal back then. As children some were sent away to live in military barracks at rather young ages. In the Middle Ages girls were married off to men at age 12. Ancient Aztecs physically tortured children for misbehaving. Not an honest spanking to correct behavior in the moment. Cactus spines shoved into the skin and held over fires to nearly asphyxiate them. Ancient Incas took the prettiest little 10 year olds away from their families because they were the prettiest and used them as commodities to become married as pre-teens to important men.
In England in the 1600s, Tudor schools whipped asses with birch twigs until bloody. By the 1700s, children as young as 5 were forced to work in coal mines. In the 1800s they were forced to climb into chimneys to clean them (a little carcinogenic, do you think?) In the 1800s, beatings in school remained commonplace, as was humiliation as a form of discipline.
And there is no evidence that any of this treatment of children produces good outcomes, relative to what is more normal today. Today we at least try to enforce high educational attainment expectations, try to offer Advanced Placement course work that will challenge the most talented kids, try to offer remedial programming that will bring the weakest performers up and give them a shot at college eventually. We don't continue to torture children or beat the ever-living **** out of them for minor indiscretions the way we did for centuries (because there's absolutely zero empirical evidence to show it produces better or even good educational, social or psychological outcomes). We don't need to treat children like special little snowflakes who are all winners, but we cannot honestly look back on history and not be disgusted by the way children used to be treated.