I think we all feel a bit this way at this time of year.
I'll be honest, I don't hate my inlaws at all but I hate staying in their house. Hate it.
It smells of mould. I'm not sure why, sort of a damp smell. It gets in your hair and your clothes. When we return, we have to air out the overnight bags and even then they still smell. My handbag now smells so bad I've switched to another to give it 6 months or so to recover. We have to wash all the clothes even if they haven't been worn, and its 2 washes before the smell totally goes, though it is significantly improved after 1. The cupboard where we keep overnight bags smells faintly of it all the time now because of the bags that have been there. I secretly keep my coat in the car while I am there so I don't have to get it drycleaned but it still smells faintly of it because the clothes I have been wearing underneath smell of it. I don't have a terribly sensitive sense of smell either. I have no idea what it is or what could be done about it, but there you are.
I don't really like the way they bring out leftovers that have been around for over a week and feed them to the children. I know they are probably fine but having done a food safety certificate I think I know too much. And she burns everything - I don't think its her fault, I think her oven is on the blink and its either stop or go. When she did sausages in the oven last visit they were so burned that even when you cut through the skin (which wasn't easy) there was no middle to them, its like it had all burned away.
I hate being crammed into a double bed with DH. We have a superking. I am completely aware that this is unreasonable and I don't expect them to provide guests with anything larger than a double bed but I like what I like. 7 nights of bad sleep is enough to make anyone grumpy about it. Last visit DH pushed me out of bed in his sleep because he thought we were at home and I was on his side. He gave me a nudge and I went flying out the bed! There's no furniture so you can't even have a lamp or a drink beside you in bed, and the wardrobes are all crammed with clothing from the 1970's that nobody ever wears so you have to keep your clothes in your bag.
A glass of wine is completely out the question so we bring our own and then get comments and sharp glances. (Well, he doesn't, but I do because I don't have a penis so I shouldn't drink obviously).
Its just that time of year to vent about it, honestly. There will be no granny dumping or going non contact or witholding grandchildren and there will be no staying in hotels because that would break their heart. They have no idea I feel this way and they will never find out because feelings matter more than these things.
At least they have WIFI now though! 