When did Christmas become the anti-Christ? Is it a sin to celebrate Christmas and indulge in gifts from Santa?

My MIL has always been Catholic but the last few years she’s become more devout I guess you could say. She no longer puts up a tree for Christmas or decorates at all...which is fine. But last night we went to their house to spend Christmas with them and so we had our 1 year old daughter too. I bought a gift for my daughter from her grandparents and wrapped it for her to open there. They didn’t buy her anything and didn’t get us anything... we gave them a card and wrapped a frame with a picture of our daughter in it. She didn’t want to open any gifts and sent the gift home with us to open there.

I’m so confused and kind of hurt for my daughter. We are definitely minimalists when it comes to Christmas (we gave my daughter 4 things for Christmas) but I feel like when she’s older she’s going to be confused why her grandparents won’t celebrate Christmas. I’m not against other people having different beliefs but I just feel sad for my daughter especially because when her older cousins were younger she went all out decorating and getting gifts when they came to town.

I don’t even know how to approach this with them and I don’t know how to explain to my daughter when she gets older why her grandparents aren’t celebrating Christmas. I just think this new movement of making Christmas out to be anti-Christ is a little overboard and robs children of the magic of Christmas. Am I in the wrong?