Has no-one in this thread looked at a magazine that was published during what was considered the real golden age for them? The ones that Meisel would have looked through when he was young?
Because magazines then were advertising clothes for adult women. Sure, the models wearing the clothes were younger than the intended audience - because being young, they had the body shape to make the clothes look their best - but the people making the purchases were not the same as the people modelling the clothes.
And people entered into an adult life at a much earlier age, getting married, taking on responsibilities. War and post-war periods forced everyone to go through some terrible things, to put it lightly. 'Teenagers' were young men who were sent to war, and if they were lucky, they came back.
The (marketing) concept of the teenager only came along later, and ever since then, fashion advertising has shifted its focus to target younger people (for reasons), so now we've come to expect models wearing clothes appropriate to the age of the model, or else it looks 'wrong', and the ideal state of existence is to be an overgrown eternal teenager with cartoon characters all over your clothes.
Anything else is 'old lady'.
And there's a misguided notion that arises, when younger people are the target of so many forms of marketing.
It's easy for a younger person to think, because companies are centering them, making them the focus of their efforts, that they must be really important - and by extension, their thoughts and opinions about the world must also be really important - when no, you're being so intensely targeted because advertisers think you're stupid, easily influenced and can be continually rinsed for your money.
When I was a teenager, I had no money to spend on the stuff I saw in magazines. At this age, now I can, but magazines don't want to sell me anything.
Fashion advertisers don't want people to progress in life to be adults, they want them to remain 'young' in mind and body, because young minds can be made to do anything.
