Why do you think the male characters don't get as much development as the females? Do you think they should get equal development?
He's the former captain of the Royal Guard, he's married to Cadance and expecting a foal with her, he was Twilight's best friend when she was a filly, he can control powerful defensive magic, he was a nerd as a colt, and he tends to get emotional on happy occasions. What more did you want from a character that rarely appears onscreen?
I mean like, have an episode that shows why he joined the Royal Guard. Or show him when Twilight was born. Maybe he didn't like her at first.
While the former is an alright thought, the latter is a very overused cliche. Regardless, the process of giving these characters more depth entails giving the character more airtime. And unless something is done very poorly, this lemma is essentially commutative. Hence, if they need to develop these characters further, they'll do so once they decide to give them more airtime. It has already been stated that there are no leading male characters in the show.