I personally agree with this, but it sounds a bit like why do things look like they were designed.
It seems pretty straightforward to ask people who believe in design to demonstrate that design is possible. If they claim the designer doesigne doesn't have to be God, then they are obligated to demonstrate that design is possible within the reality we inhabit. In other words, they are requited to do the same kind of science that people in other difficult disciplines are required to do. This could include meteorologists, experimental psychologists, ecologists, linguists. ID needs to accept the need to establish predictive relationships. That needs to be their focus.
Of course, mainstream biology is already doing this, particularly in agriculture and medicine, but that's another story.
I will be honest about my expectations. I do not believe it is possible to predict emergent properties. I do not believe it is possible to predict very far into the future of ecosystems. I do not believe allele changes are designed with foreknowledge of their effects. But I'm willing to risk being wrong.