And how old are your sisters? If they're quite older than you then it may be a generation thing. They probably consider LBT for babies, so the "they're ugly" comments are directed at you because they feel you're getting too old to like cartoons.
Big deal. I have elderly relatives (80-90+)who love LBT, Disney, and Dreamworks animated movies. No complaints there, and you'll never catch any of them telling a kid, no matter what age, that such are for babies.
Then again, beauty's in the eye of the beholder. You know what pleases you. Their loss, your gain.