Dad won't give blessing to get engaged until HE thinks we're ready, help!!!

Hey! Background: I'm 23, graduated, working full time, just moved into my first apartment. My SO is 21 almost 22 and finishing up his senior year of college with plans to continue schooling afterwards. We've been together 3 years and have known for a while this is the person we want to marry. It's important to us that we have our parents' blessings before getting engaged and married. We have his parents' blessing but when he went to ask my dad he said not now and told me that he doesn't think my so is mature enough or ready to be a husband. While I know we're on the younger side... What can I do? We were hoping to get married some time next year :( my dad said that I can elope and do what I want...but I won't have their blessing (or financial support for a wedding is my guess). I want to respect my parents but it just doesn't seem like it should be up to him like that... please advise!!!