His ability to be flawed IS limited. There are things he just wouldn't do. Are you saying that he should be capable of doing anything at all? A long time ago, he was so out of his mind because of a fever that he almost robbed a jewelery store to get a present for Gwen's birthday, but he stopped himself. Should he have robbed the store anyway, since that was drawing another line that he wouldn't cross?
Besides, there are people in the real world who never drink at all. Are none of them flawed in any way? And those people don't have to worry about what a person with super strength and no self-control would do. Peter doesn't stop having super strength at weddings, so he can't tell himself "It's a wedding, so it's ok." Yes, responsibility is something that he strives for, but this is a step he should be far past.
And "most guys?" Do over 50% of guys in the world really have sex with someone they don't like after getting so drunk that they can't remember it the next day?