I have been on the opposite side of this rocky shoal with my own mother-in-law. She sends gifts randomly. Sometimes, they are tacky and odd. One year I got a strange knitted garment that became a legend in our family that we call “the sleeve,” which is all it seemed to be. Other years, I got something thoughtful and tailored to my interests. Some years she sent large gift certificates. One year recently, she sent my husband a gift and not me.
BTW, echoing many other women on here, she would never have gotten any remembrance on any occasion if it were left to my husband. I also had to be the one to remember, come up with something she might like, wrap and ship. I did make him at least write his own thank-you note (which wouldn’t have happened if I said nothing). To add to that, left to his own devices, she would never have seen him. I was the one who said, “It’s time we visited your folks.”
Back to my original point, for years I let her seeming indifference and inconsistency hurt me. Finally, I decided to do what I felt with regard to giving her a gift and to expect nothing from her. That has made me much happier and feeling freer.
Since you say that your relationship is otherwise good, I would chalk this up to different holiday expectations and traditions.
One final two cents worth: If they are adults with children, I say it is more than time to announce you will buy gifts (or one gift) for the children.
I wish you peace.