Actually, in the original Christian form of the observance, people would dress up as both saints and angels and as devils…a reminder of the implications of our inevitable deaths. I think people would dress up as personifications of Virtues and Vices, too. Sort of a morality play let loose, by what I gather.
Nevertheless, All Hallows Eve and even All Saint’s Day and All Soul’s Day were a Christian co-opting of a pagan observance in which the spirits of their dead were thought to be especially close–the European nature religions set the date and the nighttime observance and invented the jack o’lantern, while the Roman invaders of the British isles added in the apple connection. It is a bit off to get our nose bent out of shape because somebody is co-opting our observance! If someone weren’t twisting it into their idea of what the day should be, it would hardly be Halloween.
I was interested to find that the Mexican Days of the Dead used to be observed in mid-summer, but was moved by the Europeans to coincide with the European observance that commemorated the dead. Even Christmas and Easter fall at traditional times of the year for celebrations…including the date of Easter being reckoned according to the phase of the moon and the timing of the solstice. That is what happens when you align your holidays with the natural turn of the year.
I think it is best to make Halloween what you think it ought to be, but let the others do with it as they will, too. That isn’t to say we have to give blanket approval to whatever celebrations the rest of the world comes up with, regardless of date. I’m saying that since we practically invented the practice of re-inventing the observances of others, we shouldn’t turn around an become pots calling the kettle black.