I actually still love the City Living Festivals, and still attend most of them regularly. (Spice Festival always, Geek Con usually, Romance Festival sometimes, and Flea Market almost never.) But that's because they have lots of different activities (except for Flea Market), good food options, and lots of new sims to meet.
But the ones in Snowy Escape definitely seemed to have potential, but were underwhelming pretty quickly. The ones in HS Years look pretty lacking, too. I agree that it would probably help if we could customize them ourselves, but unfortunately that doesn't seem likely to ever happen.