with the right culture and support there is nothing wrong with getting married early.
the problem comes from arranged marriages, especially if there is a large age difference.
instead of setting a minimum age, which does not help much, it should be easier to refuse, and even if agreed, it should be possible for anyone under say 25 to simply have a marriage annulled or a divorce if there are obvious problems (such as the age difference).
but if both are young, then marrying young has its benefits. the younger we are the more adaptable we are, and that helps to build a relationship and makes it easier to get along.
the idea that we should be fully matured adults before getting married doesn't actually work, because living together is part of the process of maturing, and the older you are the more difficult is it to develop certain skills and attitudes that you need for a successful marriage.
in china, people get married much earlier than in the west, but they also have strong family and social support for doing so.