It’s human nature to follow only young influencers? That’s a weird claim. Sounds like we take the current situation and justify it afterwards by saying “that’s human nature”.
Marketers have known this for years before the appearance of "influencers" - youth sells, and a young women have better cross-gender appeal than young men. Go ahead an open any pre-WWW paper magazine, count the number of women vs. men who appear in the adverts for non-gendered products
And the commenter didn't say "only". Yes, people follow non-sexual influencers all the time, but it's much easier to get followers if you're sexually attractive.
There have been plenty of times during history during which nobody cared what young people thought. I'd venture to say the majority of it.