I think NAH, tbh.

Why is the burden on her to translate? He married into her family as well so why can’t he also try learning French? Or rather than bailing out on dinner, start speaking to his in laws in English and see how they respond before cancelling all future interactions with them? At least then, he is putting in more effort twiddling his thumbs and be grumpy about it. OP has not once indicated trying to compromise.

Damn, if op hates sitting at dinner listening to French, he would not survive my in laws. They will naturally interchange out 4 or 5 languages without knowing. I don’t sit there and complain. I chose to better myself by learning some of the languages. It doesn’t hurt to learn new languages.