I have a similar story. The first year that we were married we went to my in-laws' for thanksgiving (and every year since, too). I asked my MIL what I could bring, and she suggested I could bring pie. I made homemade pumpkin pie (like my mom makes). The recipe makes 2 pies, so I took them both, even though there were only going to be 5 of us at dinner. When we got there, MIL *also* had 4 pies (store bought), including 2 pumpkin. There were 5 people and six pies. She claimed that someone at work was selling them for charity but felt like she had to buy them, but four!?
The next year, she suggested that I could bring cranberry sauce. Again I made my mom's homemade cranberry relish. It's a pain to make, but it's delicious. My MIL sighed when she saw it and said "I think I have a can in the pantry somewhere." And nobody else ate mine.
I have determined that they like what they like and don't appreciate anything else (even if it's "better.") Now I take green bean casserole with the nasty french-cut green beans. I refuse to eat it (and I dislike most of the other stuff too), but they like it.
My mother-in-law, back in the days when she was still hosting family holidays, was like this as well.
For example, if I offered to bring a sweet potato casserole, she'd say, "That'll be great!" And, then, we'd get there w/ my sweet potatoes, & she'd have made some sweet potatoes as well & would tell me something like, "I didn't know if you'd change your mind, so I went ahead & made some too."
One year, for Fourth of July, we were bringing the chips. We got there, & she had 5 bags of chips on the counter - "There was a sale, so I went ahead & got them. You can just save yours & take them back home."
If I decided to just a bring a dessert, it was complete overkill, because she'd always have 3-4 other desserts.
And she always went for quantity over quality - store-brand chips, store-brand soft drinks, canned green beans, 5 pies made w/ some variation of Cool-Whip & pudding.
It didn't matter that I may have spent tons of time on a homemade cake or the sweet potato casserole.
I basically quit trying. LOL!
Over the years, I learned that were 2 things I could make which were actually appreciated & she wouldn't duplicate - a sausage & wild rice casserole that I'd make for Thanksgiving brunch (she'd have bacon, sausage, & ham already, so my sausage & wild rice casserole was really just adding more meat, but she & my FIL both LOVED that casserole & she'd even save some leftovers for herself) & my strawberry pretzel salad at Christmas.
If I brought anything other than those 2 things, she'd go ahead & fix either the same thing or something very similar. But I could always count on my sausage & wild rice casserole & my strawberry pretzel salad.
EDITED TO ADD: I forgot about the year my SIL (DH's brother's wife) hosted Thanksgiving. We were getting together the weekend before Thanksgiving, & she had decided on more of a "lunch" menu. She & my BIL were roasting a turkey & getting a ham & wanted to serve it w/ bakery rolls for sandwiches. So she wanted more lunch-y type stuff & finger-foods to go w/ it.
So my other SIL & I brought veggie platters, pasta salads, baked beans, chips, etc.
Well, my MIL decided we hadn't planned a Thanksgiving-enough meal, so she came in w/ casserole dishes of dressing, dumplings, sweet potatoes, some kind of potato dish, green bean casserole, her own fruit salad, a pecan pie, one of her Cool-Whip pies... It was ridiculous, & my SIL had no where to put everything!