Expecting "realism" and coherency from a fantasy world destroys the fantasy. But somehow projecting realism onto fantasy is a popular activity for fans.
I don't know about realism, but coherency is absolutely required for any fantasy world(imho).
As long as everyone is on board you can kind of do whatever the hell you want, like playing with legos and toy cars and whatever else is on the ground as a kid. I’d venture to say it’s also why “rule of cool” is so popular. Sometimes you just want to do cool/funny/etc. stuff and D&D told a lot of people “hell yeah get after it.”
But of course if you expect consistency where there is none to being with you will likely be disappointed.
Perhaps that's partly why the attempt by a different author to build prequels failed so spectacularly, too, because it assumed too much the world was internally consistent and so was boring and didn't reveal anything truly new because it wasn't really trying, it was just playing out the obvious consequences for if you believed in some of the consistency of the previous books. I suppose that it didn't really understand the onion it was trying to emulate and that there should have been a lot more lies and a lot less consistency.
(ETA: It's also why sadly it felt like the last five books were all gearing up [often literally, new equipment every stage like levels in a videogame] for a war that will now never happen, because we don't know with who and for what reason or why because the lying protagonist wouldn't tell us, probably because Zelazny hadn't yet figured it out either and was waiting for the right moment to strike in the books that would have followed in some other timeline freer from cancer. I do still wonder where those books would have been leading. I don't know the author that could answer that definitively for us other than Zelazny.)
What don't you find internally consistent about Discworld?
Yes, it's full of gags and references to the modern world, but is that inconsistency? Or do you mean something else?
I find the strongest differences are between early and later Pratchett, but there are big streaks of consistency across novels, especially within a "sub-series", e.g. all the Watch novels, all the Witches novels, all the "industry" novels, etc. Even they are often consistent across subseries.
That's why I think Discworld is surprisingly consistent, all things considered.
That certainly isn’t the case for The Lord of the Rings and the rest of Tolkien’s development of his world.
https://nathangoldwag.wordpress.com/2024/05/31/the-moral-eco...
The Shire is, in basically every respect, including its economics, an idealized version of the English countryside.