“For thousands of years Jewish parents married off young children. Apparently they were fine with the maturity, and so should we be. Maturity grows with time, as it did with our zaidas and bubbes.”
Actauly Tosfos in Kidusin had a hard time with the practice of picking a spouse for your very young child and went on to explain that the reason is because “kol yom hatzaros misgabros” meaning it was a dire situation that forced people to act in a non ideal way.