The allegory is accurate, as far as it goes. Our information must be processed through a sense organ subject to natural errors and biases, so of course no one person can see the object clearly.
Extending the analogy however, we do have a means of figuring out the clear shape of that object. Rigorous thinking combined with shared and competing observations allow us to infer the true shape. There is a reality out there, a true shape, and we do have the means to figure out what that reality is, albeit slowly, piecemeal and over time. Empiricism and science is the only reliable means.