The correct answer is - Each theory is a different eyeglass through which to look at literature.
Regardless of the literary theory you are using, there will be many different interpretations of one single text. One person may have one analysis, whereas you may have a completely different one, and you may be using the same, or a different theory.
A theory cannot give an exact interpretation of a text because that doesn't exist - everyone can have their own interpretation. Theories can help you analyze a text and you should use them if you want to. Not all theories are complex - some are really easy to understand.