Most supposedly medieval fantasy is, in fact, a mix of medieval and then something much more modern, like 18th or 19th century. It's because pure medieval is quite gruesome. Stories like "Karate Survivor in Another World". It gets ugly and thus wouldn't be exactly what most readers want to see. Of course it's even more veered toward the modern aspect in fantasy romance because the FMC wants to enjoy comfortable, lavish life, beautiful dresses, extravagant food, and all that stuff. In shounen/seinen fantasy, adventure and fights are emphasized, so the city life doesn't need to be quite as luxurious.
Sometimes it seems like the only thing medieval left is the lack of firearms, steam engines, and other such technology. Feudalism remaining in some series could also be counted as a nod toward medieval times.