I certainly agree that Weezer are power pop, the thing is that power pop itself has a bit of an odor of juvenalia about it. It’s music meant to remind you of being a wide-eyed 15 year old kid. I doubt many 40 year olds like myself are going around telling people “I just love me some power pop”

I think the basic idea is using loud guitars to play sugary melodies, is a good “core” definition.

If anything, Big Star didn’t actually do that much “power pop,” they were more like the precursor to 80s jangle pop.