A human is needed to show how app’s technical features are relevant to a particular audience with a shared social context. As the LLM is not (and should not ever be) a participant in that social environment, any marketing it generates will almost certainly land as tone deaf or presumptuous.

That’s the “human in the loop” part. Use the LLM to generate a copy and the human to refine it.

If you think successful campaigns these days are always entirely done by humans, then I’m afraid you’re mistaken.