If complex or information-rich things require explanation, critics ask why the proposed Designer does not also require a designer. Appealing to intelligence may seem to move the explanatory problem back one step rather than solve it.
The objection raises a question about ultimate explanation. A proposed cause should not simply create a larger version of the same unexplained problem.
However, a design inference does not necessarily claim that everything complex must have been designed. It asks whether particular observed effects are best explained by intelligent causation. Discovering that an artifact was made by an intelligent agent does not require first explaining the origin of that agent before the inference to manufacture can be reasonable.
The further question of the ultimate origin or nature of the Designer remains important, but it is distinct from the narrower question of whether intelligence contributed to the effect being investigated.
If intelligent causation is inferred, what can the evidence tell us about the nature, origin, or necessary existence of that intelligence?