Do you mean that your interpretation needs to be stronger, or that the wording of your interpretation needs to be stronger?
If the former: locate the fulcrum of the text - in other words, the main message on which the other themes etc rest. This will be your point of reference when discussing the radiating themes and messages. Then branch out into what those radiating themes and messages are.
For example, I think that the nature of humanity (what it means to be human, the limits of what humans can and should do, etc) is the fulcrum. The theme of usurping the role of God (biblical allusions) feeds into it, as does the theme of fear of difference/the unknown; responsibility for one's actions and the responsibility of the master/parent/scientist towards the slave/child/creation also link, as does the question of what turns humanity inhumane or monstrous.
If you mean the wording needs to be stronger... well, you need to figure out exactly what you mean, first. Content comes first; wording comes second.