I agree with a lot of what you've said and you make some very interesting observations, but I'm not sure Pratchett's message is that grim.

He does criticise the way we use stories, but I don't think he wants to paint a bleak picture of stories. After all, stories are what he uses. The narrative force is what binds the Discworld together. For me personally, the point was more that what we often forget what lies behind the stories. The reason for them, the purpose they served, the time in which they were conceived.

I saw this in the greedy kid fixated on presents and all the rituals (singing carols, christmas trees etc.) that have somehow usurped what they were built up around. All these rituals are after all only concrete representations of the focus on family unity and generosity.

I think Hogfather is Pratchett's way of asking us to look at the stories in our lives from a new perspective.

I do, however, think there is a sense in which his answer is that humanity as it is today, as exemplified by Teatime, is not capable of appreciating the unassuming charity in some of those stories. He does, to some extent, the validity of our tendency to deem some stories naive.

I can't help but ultimately come to the conclusion that the fear-driven legends and myths we surround ourselves with are more symbols of what we as a race have become than they are actual stories.

I am afraid I've started rambling now, but that tends to happen when I triy to wrap my mind around interesting questions. I must re-read this book some time.