It's a game, one I don't play, but if you ruin kid fun of course you'll get eyerolls... regardless of your background.

My recovery is just to own it, and say that I may not believe anymore, but "I'm proud of you sweety for believing". Kids won't take that as condescending cause the notion of Santa disbelievers is built-in.

I think my kid flat out told their friends at pre-school that Santa Clause died. Which lead to some very interesting conversations. We watched the cartoon film Klaus on Netflix (would recommend) and that's how they internalized it. =)