It's a bit late now, child.
to extend it a little, add your opinions on the ways genre changes over time, how one genre borrows aspects from others, how authors can use some conventions, subvert some, an ignore some, and if this is effective. Then in your argument use examples from the texts and comparing texts to back it up, even to the point of saying "it's this xxxxxx that makes Y text more effective than Z text at ...............(reaching audience, conveying meaning... yada yada whatever your argument is).
You could include things like what neccessitates genre's flexibility eg. changing expectations/ desensitisation of audience to violence, changing perspectives in society and changing political and social context. And, if relevant, what aspects remain the same throughout.
If you do not have opinions at this late stage, make some.