^ I absolutely agree.
If your main feedback is that your ideas are too simplistic (rather than that your writing is crappy), I 100% agree to stop writing a standard expos or essay (unless you're not doing that, in which case different advice is needed!).
An expos or essay has all the ideas on the surface - explicitly. So it can be difficult to make them sound complex or sophisticated.
Something more 'creative', on the other hand, has most of its context (eg I&B) ideas and arguments kind of hidden under the surface. The risk of this is that the examiner won't find them; the benefit of this is that any ideas they do find will kind of be partly their own wording (because they have to interpret them). Which means markers are often less likely to think they're superficial.
Yes, you absolutely have to make sure that whatever you write HAS ideas that can be found under the surface, and if you write a story it has to be a great story on its own terms - or a speech has to be a great speech on its own terms, etc - but switching to creative is a little trick that often helps overcome the problem of 'ideas too superficial' feedback.