Considering I'm the same height as I was when I was 17, with a bit of make-up and different clothes, I could pass for my younger self. At least he's not like...10 years senior of his character.
And it's not like they can't add things to the newer movies for explanation, I think they should have just done it sooner with the first 5 movies. It's ok to have a movie that's 3 hours long! No, I do not want to sit in a theater for more than that, but would I have gotten the DVDs with all the stuff you had to cut out? HECK YES! It would satisfy my nerdish tendencies! (And no, a few deleted scenes that you can watch in the extras section is not an extended version.) I know the constraints with translating a book into a movie, but there are some key things in every one of them that there was plenty of time to explain. GoF would have been better spent explaining the Crouch's instead of having some long dragon chase which was about a page in the book. The first two movies were more successful because the books were shorter, so cutting stuff was easier, but when you cut things, it's kind of silly to cut or change the things that really matter.
Oh, and if they play up the Dumbledore being gay thing in the last movie, I will find the director and the screen writer/s and slap them for their shenanigans.