To be honest, I’d not be really pleased if someone bought me a cheese grater for Xmas either.
im not sure why folks struggle so much, it is so easy. If you don’t know them well enough, as the op clearly doesn’t her mil. Then There are very few people who don’t appreciate one of the following, a luxury shower gel, an expensive bottle of wine, port or spirit,, a great box of hand made chocolates, a luxury cheese selection , a box of hand crafted fudge, a Xmas hamoer of drinks and sweet stuff or savoury stuff.
very few people, eat no sweets, no chocolate , no cheese, no alcohol, and never wash. Sure some, before anyone shouts my minging mate likes none of that, but the majority like at least one thing on that list.
just think of what they like and buy the luxury version. A treat they’d not normally get themselves, the luxury version of what they actually like.