I think that question was borderline. It really needs some more details to be a good question, but I think it's still clear enough as is. Without the additional information, like why the person doesn't celebrate birthdays, it could be considered unclear, because that detail can and probably will change the answer set considerably. That said, I think too-broad would have fit better than unclear.
I think this is an example of the way questions are being judged, at best, inconsistently on this site. While this question was closed, a very similar and much more problematic question was left open. I connected these two questions because the question you're asking about was "answered" by the author of this more troublesome question.
Then there was the OP's answer to their own question:
I am choosing to disappear on that day. Sorry! I do not have the courage to tell them to cancel the party. They are losers if they are planning to celebrate on the day when I do not even show up. They do not know that I knew they are going to throw a party beforehand. So clearly it is not my fault! Good luck, losers!
And the comments the OP left under a couple of the other answers:
No, I am choosing to disappear on that day. I do not have the courage to tell them about it. They are losers if they are planning to celebrate on the day where I do not show up. It is not my fault. Or is it? – VadaCurry 2 days ago
How to politely turn down my surprise birthday celebration at work?
I think it's worth thinking about being more consistent about what sorts of questions should be closed, and why we're closing them.