I feel like a big part of this is because the Disc isn’t just a fantasy world where they have condom factories, but a fantasy world where condom factories are actually relatively new. The inventor is (was) still alive, and his products are still somewhat controversial.
In most fantasy settings, The Magic Is Going Away basically means “the world is going to be the same medieval cesspool it’s always been, but now you won’t even have a friendly neighbourhood wizard to cheer you up”. You don’t see that many fantasy settings that change beyond occasionally getting rid of the old ‘evil’ ruler and bringing in a new ‘good’ one.
Discworld, on the other hand, progresses. Over the course of the series (which appears to be only about a generation or two, in-universe) we basically see Ankh Morpork go from a Stereotypical Fantasy City to a Functioning Society.
We watch them develop newspapers, a police force, a postal service, what amounts to a telegraph system, and a railway network. We see dwarves, trolls, vampires ands goblins slowly gain acceptance. The Mended Drum goes from being baffled by the Disc’s First Tourist to holding choreographed bar fights.
And there are moments where people mourn this.
One of Cohen the Barbarian’s main purposes as a character is arguably to mourn this shift from an old-style fantasy world to a society with real world implications. The short story ‘Troll Bridge’, where he goes out to fight a troll and ends up reminiscing with him about The Good Old Days when heroes used to fight trolls, is a great example of this.
Angua worries about the melting pot only melting one way and erasing the cultures of fantasy creatures. The dwarves have a whole movement to try and preserve the Old Ways, even as their children embrace the New Ones.
In ‘Shepherd’s Crown’, right after we just had a whole book about how wonderful the railways are for the Disc, we have Tiffany Aching’s father wondering if he’ll be the last Aching to own a farm on the chalk (and have that family’s semi-magical connection to the land), because Wentworth would rather be an engine driver.
There are several moments throughout the series where characters do stop and look back at how things used to be, before everything went Modern, and feel some sadness about the things they’ve lost. But the series is also very clear about the things that are gained.
And that’s what I think makes it so realistic. Progress rarely does go all one way, and some things are always lost, but most people accept that you can’t spend your whole life pining after the elves (who were never really as nice as you remember them) when the city needs condoms.
