Besides some quality of life updates, like alerts for Sulani's festivals (I have yet to catch one because of that; I never live in the main town), I think the best thing is to have something that makes them more unique and/or overarching goals.
I like the idea of festivals anyway, but I rarely have much incentive to visit the same one more than once with a family. CL's festivals at least have the food stalls for recipe collecting as an overarching goal, but in general one spice festival win and there is no need to go (one of my favorite festivals, though, but it is pretty well all the same). The slight exception for me is the flea market festival just because I like to see the random stock for sale, but I would not really call it the most fun festival even if I attend it often. They are all fun for novelty's sake and they do have some gameplay, but it only goes down hill after CL's.
I think SE tried the overarching goal thing with the Simmi collection, but it just is not as motivating for me. Plus I think there may be some Simmis that cannot be found through the festival route, which kind of defeats it as a festival goal. I do enjoy the atmosphere of SE's festivals, but they do need more to do than eat and socialize. I agree ice sculpting or something for the Snow Festival. I would love if we actually got to release laturns or something else interactable for the Festival of Light. Some kind of traditional dance would have been amazing. It might be kind of one note, but I do enjoy the voidcritter aspect of the Festival of Youth. I would have loved to have seen it expanded, but at least it has it.
As for IL's... I really need alerts to catch them to critique them. However, I imagine they are light on gameplay. Something like a fishing contest or anything would at least give us something to do. Maybe for collecting seashells or diving. Even a sandcastle contest. Something.
