That does not make it correct. Muslims literally do this same exact thing you are saying, marrying off their teenage children and letting them bear offspring. That is in no way healthy or ethical. Just because sth was done " long ago" that doesnt suddenly make it a good example to follow.
Of course, during teenage years we are all horny, but does that mean we should just go and fuck people left and right, or suddenly make babies? No it doesn't. Doing that would only show the failure of our parents of keeping their children safe from STDs, unplanned pregnancies with malformed babies, broken hearts, disturbed minds and angry families.
I keep reading in the news about how especially in the bible belt in the US, along with pedophilia, theres also some teen relationships that lead to pregnancy at ages like 13 or 16. That's not correct. The body of the mother and father, their brains and minds must mature first if they are to have a good life together. It's not my business what others do, and i never said that teens can't be in relationships together, but surely you cant afford your own kid to sleep around with multiple other kids, that'd just be irresponsible.