Home alone has to be set during Christmas, these are crucial parts of the plot:

• The entire block travels at the same time
• Houses have decorations, which are used as traps
• Houses have lights that turn on at a specific time
• It has to be set during winter

So if you could have a different holiday during winter where lots of people decorate their houses to turn on lights at a specific time, then it wouldn't necessarily be a Christmas movie. Otherwise you need to change crucial points of the plot.

Other examples are Jingle all the way or Nightmare before Christmas you can't change the Christmas theme in those movies. I mean, you can but you'll end up with a very different movie. Whereas if you change Christmas on Die Hard for any other party event only the decoration changes, the plot of the movie would be essentially the same.