for my experience , in my region , the women recently in 100 years ago was , married at 12 years old , and they were "mature" (mean able to marry) , and my grandmother married at 12 years old , and my mother married at 15 old , now it's different , the 15 old could not marry !!!! ????
I the case of Prophet Muhammad (pbuh) God , maybe god want that , He is messanger of God , the God sent him to the mankind , if God did not allowed him to married 11 women , he would not ,in this case you are judging the god choice , and deny it !!!
for eg : Solomon (pbuh) as i heard married more than 500 wifes , God allowed to him,
-You don't have the right to judge the God choice and God law