I don't think I've ever lived in a neighborhood where carolers sang at the door or in the common ground. I'm not sure how I'd react if that happened today. Most likely, if the vocalists sang tasteful carols at least passably well, I'd probably smile, applaud, or say, "Well done. Thank you."
I'm not sure I'd acknowledge even a stellar rendition of "Blue Christmas," though. We all have our limits, and that's one of mine. Try as I might, I just can't get past such overly fretful lyrics.