Just Add Magic
If a genre doesn’t have enough viable niches, the easiest way to address the lack is to just add “magic” to the setting. I’m using “magic” broadly here, to include all forms of paranormal and supernatural phenomena, including psychic powers, superpowers, mutations, cybernetics, impossible tech, and so on. Examples include:
Deadlands: Western + magic
Ascendant, Champions: Crimefighting thriller + magic
Call of Cthulhu: Mystery story + magic
Gamma World, Rifts: Post-apocalyptic + magic
7th Sea: Pirate adventure + magic
Shadowrun: Spy thriller + magic3
Vampire: Underworld drama + magic4
Weird War II: War movie + magic
That games with “magic” in them are more popular than games without magic is commonly known among TTRPG game designers. But it’s not often explained why this is the case. There’s nothing magical about magic. It’s simply a versatile tool to create a lot of niches.
The problem with “magic” is that its inclusion changes the feel of the genre. At its best, it can lead to the development of a new subgenre, which develops its own tropes. More often, it descends into gonzo farce. At its worst, it can destroy the essence of what made us want to design for the original genre — the grit, the realism, the struggle.
And yet magic works. There are virtually no commercially successful western, mystery, crimefighting, post-apocalyptic, pirate, spy, or underworld RPGs without some form of magic. There are plenty of examples with magic.
Is that it, then? Are we doomed to include magic in every genre? Does every player’s need to be the special snowflake mean that we can never create a commercially successful Western RPG, or Pirate RPG, or any other RPG, without magic?