Expectancy, maturity and responsibility have changed greatly in the past few centuries. First, when you look at a recommendation to marry young, life expectancy before the 1700’s was 25-30. By 1900, it jumped to 40. By 2000, it was 68. So where you needed to have children by 18 to raise them, you can safely delay that to 30.
At one point, all men learned a trade by working it, all women learned housework and raising younger siblings from helping. Most people didn’t get a formal education. Even when they did, they were required to run the family business while studying. Now with the Industrial Age we have the ability to raise learners instead of workers. But instead of just learning your father’s trade, you are required general knowledge. A woman who previously learned to raise a household now takes on a career to support the family.
Needless to say, we don’t need Shidduchim at 18–19. Delaying marriage and children by just 2-3 years will allow men and women to learn and earn, which will help their family in the future.