I agree with you OP and think you were perfectly clear - no issue with people who just don't, for whatever reason, fancy christmas parties and who, if asked in rl, say, 'Nah, sorry, can't come.' (end of conversation)
What's annoying are the people who deliberately choose to click on a christmas related topic on a forum with thousands of other conversations to choose from and start the sneery 'Spend time with colleagues??? No I have much better things to do! Can't think of anything worse than listening to loud music! In a public place! With other individuals! Amidst the presence of alcohol and forced jollity! (shudders and visibly pisses on the chips of everyone who does enjoy parties and leaving no other possible interpretation than that you are somehow less refined/lack in social skills if you rely on companionship from your colleagues/are a bad parent for not spending this time with your family....)'
It's not just christmas parties though - I find the same people tend to look down on almost any form of socialising. It's lame to be friends with your colleagues (despite the fact you have at least a number of other people, likely similar qualifications, and ideally at least a vague interest in whatever your field is, in common). But people also roll their eyes at the idea of being friends with school mums (who, again, you have at least a fair amount in common - similar ages, children of similar ages, worries and achievements of said children). Some people don't even seem to like being friends with their actual friends, if the amount of sighing and eye rolling about being expected to attend a hen party or similar on MN threads is anything to go by.
I do wonder sometimes who these moaners actually find acceptable to be friends with?
And then these people blame it on not being extroverted - as an introvert myself I find it insulting. It's perfectly possible for an introvert to have fun, even in a busy party setting. There's a big difference between 'introvert' and 'moody git.'