I think the concept has some validity, but the evidence doesn't line up. If there was an intelligent designer, then looking for designs that can only be done through intelligence would be evidence for such designer, so the reasoning on that part isn't wrong. It's just that every piece of evidence to support it is weak and very questionable. The challenge really is to prove that something was indeed designed with intent and intelligence.
Claiming there are link between nature and Designer, by conjuring up the imaginary intent plus intelligence, will only leave impossible task of testing their incredible claims. And with the Designer being the agent for the designs, it only revealed that the Designer to be itself the weakest link.
How would they propose to make observation of invisible Designer?
Because that’s the heart of what “evidence” is.
Evidence is observation where any scientist can observe/detect, measure, quantify, test/verify/refute the evidence for their proposed model.
That’s what ID proponents can’t do, especially with this nonexistent Designer. How to do they observe/measure/test something that’s invisible and incorporeal?
And the invisible and incorporeal Designer sounds like another entity with the same attributes - God.
The Designer sounds as implausible as ghosts, ghouls and goblins, zombies, fairies, leprechauns, rainbow-farting unicorns...