Thought on Shutter Island

An idea occurs: Shutter Island as metaphor for the cinematic experience. "Disappointing ending" intentional. Conveys Scorcese's disappointment with audience for continuing in their delusions? Shows Heroic resolve to continue holding to your beliefs despite the voice of authority telling you to abandon them? Metaphor for the demise of the left? Hallucination represents the cinematic experience. Creating an illusion for an audience. Trying to create a healing illusion? Trying to convey truth to the audience via illusion. Then what is the issue? And is the thing successful? And how to interpret the ending?