DH and I are both only children. DH's parents died years ago so it's literally just my parents left. They are in their late 60s/early 70s and in fairly good health. We live quite far from them (full day's drive, about 8 hours.) We have two young DC (1 and 5) and we both work full time, so we don't visit very often - usually 3 times a year including Christmas. I've always felt guilty about that but we can't manage more often. We would happily see them more often if they visited us, but even though they are retired whereas we are constantly busy and feeling like we're juggling too many plates, it has always been "our job" to visit as I was the one moving away and they will not stay with us..
Since retiring and Covid, my parents have basically become recluse, they don't see anyone, refuse to do video calls (despite us buying them a smartphone and showing/explaining how to use it) and when we tried to invite them on holidays with us they bailed at the last minute leaving us with their bill. However they complain that I do not call them often. I really struggle with voice-only calls especially as I'm always walking on eggshells not wanting to say something that will offend them in some way. Still, I have never missed Christmas with them (except during lockdown when they told us not to come) as it's important to me and now to my older DC.
Yesterday I got an email from my father saying he came down with the flu on Saturday so they are cancelling the Christmas get-together as the contagion risk is too high. I said I hoped he would feel better soon, but as we're all vaccinated against the flu and not at risk we're happy to take our chances - anyway hopefully he will be better after a week! Of course DH and I offered to cook, do groceries and stay at a hotel as we suspected it was the additional work they were worried about - no problem with doing any of these things.
They still don't want us to come and the reasons they give (without going into details) don't really make much sense. I wouldn't mind so much if they were honest about why. As it is I just feel sad. My 5-year-old has been looking forward to going to "grandpa and grandma's house" for Christmas. From a purely financial standpoint it's also too late to cancel the cattery so we'll be paying that anyway. AIBU to be sad and annoyed? I don't remember either set of grandparents ever cancelling Christmas when I was a child.