As rk-47 said
actual gameplay not a click next see erotical content program or glorified gallery.
Next Step would be to
integrate the ero part into the gameplay. Like Erotical Night did.:
https://f95zone.to/threads/erotical-night-v1-5-e-ohkoku.2362/
(Simple RPG where you fight girls turned into Succubi - you have to make them come to save them.)
Otherwise you might as well play chess online and everytime you win you go to a porn or hentai CG webpage.
Some
choice - the you run into someone and sex happens really takes the game out of a sexgame (unless your game is all about playing the one that non-consential stuff happens to) - especially bad if it happens in an obnoxious you have to do exactly as you're told tutorial with a lesson that could just be explained with a couple screenshots and a few lines of text in the release post.
Character creation and customization. Even if it's very basic and superficial like a couple hair styles or starting weapons I'd like some choice concerning the main character. Several options in many games' settings and Nutaku's entire seperate gay section would be obsolete if you just had the simple choice of stating your sex and what you're into during character creation.
Sandbox option - I really like if you can just keep playing after the story or as a seperate game mode.
Nice flow (quality and quantity) of ero-content. If you can't wank playing the game the ero nature of your sexgame is only of secondary nature which means it's really a regular game (like the Witcher with its card collection mechanic) then the game won't be judged by it's ero parts but as a normal game and well in that case this forum wouldn't really be the place for it but just another tangential option to advertise it.