A motion to dismiss asks the court to end a claim on the pleadings, before discovery. The court takes the complaint’s well-pleaded factual allegations as true and asks whether they state a claim the law recognises.
That framing decides what arguments work. “The plaintiff is wrong about what happened” is not an argument on a motion to dismiss — that is a fact dispute for later. “Even if everything alleged is true, it is not a breach” is.
Legal conclusions dressed as facts get no such presumption. A complaint asserting “defendant owed a fiduciary duty” without facts from which one arises is vulnerable; one describing the relationship that created the duty is not.
Partial success is common and valuable. Knocking out two of five theories narrows discovery, reduces exposure and changes settlement posture even though the case continues. Dismissal is also frequently granted with leave to amend, so the realistic goal is often to force a better-pleaded complaint that reveals the plaintiff’s actual theory.