That's not the sign of maturity you're making it out to be.
Don't forget the issue where he organized a topless pool party at the Playboy Mansion!!!
You're right though, he should have ignored what MJ said, and forced her to stay in a relationship with him.
I'd also say that during Straczynski's tenure, Peter was written older than he had been previously. Paul Jenkins' Peter Parker in the sister series came across younger. in the earlier ones at least. Swings and roundabouts.