I think one of if not the main reasons the medieval era has such a big hold over western fantasy is that it’s a pre modern time . Fundamentally strange, alien, and perhaps unknowable
Ttrpgs are for me about exploration, seeing somewhere new and interacting with it . Combat can be interesting if done well, as can improv-type social games, but encountering the bizarre where it’s at imo
The past is a foreign country, and one rich with detail. It’s easier maybe to create a convincing place that breathes out of the past than to imagine and project one from the present? I’m not sure. Fantasy does seem to be bigger than SF in the broad sense though
Maybe because the premodern past is wild but still easily legible
But the modern era has lots of good stuff! There are plenty of weird realities in the present and and future. Guns. Propaganda. Spaceships. None of that in the mud grubbing Middle Ages