Sex is obviously the most important element to the game and if it wasn't present most players wouldn't play. But if it's not all about sex though. Not for the player nor for the protagonist.
For the protags it obviously depends on how the player shapes them, but even in the most hedonist playthroughs the protags will have concerns besides getting laid.
For the player there is a level of investment into the characters and their relationships. Again not necessarily the most important thing for everyone but players do generally care, otherwise everyone would just make pure slut playthrough where Ian and Lena fuck everyone. There wouldn't be dedicated Alison or Cindy saves. Because the players would only care about maximizing the sex happening. If it was just about sex everyone here would not be playing a narrative game and instead load up pornhub.