The title and the question here are two different questions. Are martial characters overshadowed to the point where casters are just better? Yes. Are they totally unable to contribute? No. Are they worth playing? It depends on what you value. I don't like D&D's magic system, favor fantasy that is borderline historical fiction, and am generally in a position to contribute with a worse character in any group I'm likely to be in. Noncasters are fine by me and I play them pretty close to exclusively.