There are some in-universe laws or facts that fictional genres cannot give up (Edit:typo) easily - one in scifi is the small crewed spaceship or even space fighter.
Even if guns exist, there is an arguable thrill to reading about a character infiltrating a castle with a saber and two pistols that cannot be reloaded easily. Long ago, those were pirate or naval pulp fiction.
Imo any setting can produce great stories, it's in how they're told not in how the world works. Established genres of fantasy are just attractive to some people, since analogues of the laws and structure of the world are already partially known - and it's possible to subvert expectations while not alienating people.
Even if guns exist, there is an arguable thrill to reading about a character infiltrating a castle with a saber and two pistols that cannot be reloaded easily. Long ago, those were pirate or naval pulp fiction.
Imo any setting can produce great stories, it's in how they're told not in how the world works. Established genres of fantasy are just attractive to some people, since analogues of the laws and structure of the world are already partially known - and it's possible to subvert expectations while not alienating people.