My issue is not that the player is led to believe that they can find a cure, it's that they cannot actively look for it. If I am playing on a friendship path with Karlach, it just makes my character look like completely uninterested in her fate.
It's all those questions you cannot ask: when you meet the gnomes working on hell engines and ask nothing, meet an experience wizard like Elminster and ask nothing (or Gale, he has been a high level wizard before losing his power, can't you try to research something together?), when Shadowheart gains enough levels to get divine intervention and ask nothing. And then it turns out that a full body transformation apparently fixes the engine. Which maybe, if you researched a polymorph spell, could have helped without costing a soul.
There is a difference between a 'tried your best, yet it was not enough' and 'didn't try much, because why' storytelling. For example, Enderal (a game based on Skyrim engine) has no good endings. But throughout the game the protagonist keeps fighting and looking for a solution.
