Two things: * I don't think polarization is a good signal for poor quality; I would rather suggest it means a more niche product, more highly focused. That the niche being served is largely adolescents is unfortunate. * I think big-budget movies have been getting more conservative and predictable, but I would hazard a guess that it's due to financial industry turmoil and consequently less desire for risk taking.
Ever seen the Poochie episode of The Simpsons? The producers try to boost the ratings of Itchy and Scratchy by adding a ridiculous character designed to appeal to everyone. Near the start of the episode they hold a focus group (text from snpp.com):
Man: How many of you kids would like Itchy & Scratchy to deal with real-life problems, like the ones you face every day?
Kids: [clamoring] Oh, yeah! I would! Great idea! Yeah, that's it!
Man: And who would like to see them do just the opposite -- getting into far-out situations involving robots and magic powers?
Kids: [clamoring] Me! Yeah! Oh, cool! Yeah, that's what I want!
Man: So, you want a realistic, down-to-earth show... that's completely off-the-wall and swarming with magic robots?
Kids: [all agreeing, quieter this time] That's right. Oh yeah, good.