Seasons expansion gave us weather. It did not give us holiday CC. If you want a sim house that actually looks like December — garland on the banister, a tree with presents that aren't recolored vanilla meshes, a dining table that reads "Thanksgiving" instead of "generic spread" — you need community CC.
This collection is the biggest one we run: nearly a thousand mods spanning Christmas decor, Halloween costumes and yard setups, Valentine's clutter, Easter decor, and the summer/fall seasonal pieces people forget exist. Creators like Syboubou, Felixandre, and HarrieCC come up a lot here, but the strength of the Sims holiday scene is really the volume of smaller builders shipping one good pumpkin set or one good Hanukkah table a year.
Use it as a seasonal swap — archive half of it in the spring, swap back in October. The grid is sorted by downloads first, so the evergreen picks rise to the top, and seasonal one-offs live further down for the specific occasion you're building for.