I think the opposite is true. The most popular porn titles I'm aware of have:Constant updates ; P
Also appealing to specific fetishes.
1. Very good production values (graphics, programming, etc).
2. Very vanilla in terms of fetishes, so they can be easily distributed on many platforms such as Patreon, Steam without playing constant cat-and-mouse with the platform's gatekeeper.
Commercially, I think it's better to go for fetishes you love (and put your soul into) than trying to win the vanilla game. If you're producing a good fetish game, fans of the fetish will find you, stick by you and will tend to forgive gaps in quality as long as they see you're commited. In the high end of the vanilla scene, the quality is very high and it's very hard to distinguish your game, especially since you're going against publishing teams who sometimes have 5+ years of experince.