The one question I keep coming back to is why would common design produce a nested hierarchy?
I'm a retired Intelligent Designer (embedded software concentration) with 35 years of practical professional experience, so I knew a thing or two about design (including common design) because I've seen (and done) a thing or two.
An intelligent designer can make wholesale changes arbitrarily (eg, replace entire modules (eg, completely different CPU, entire sections of code (object-oriented programming (OOP) is explicitly designed to do that), switching to an entirely different language, replace a car engine with an entirely different engine from a different manufacturer (eg, our Plymouth Voyager minivan which had its American Dodge engine replaced with a Japanese Mitsubishi engine)), port totally new technology from another "designed hierarchy" (eg, replacing hard drives with solid state drives, replacing serial ports and parallel ports with USB, wifi, and Bluetooth, replacing proprietary iPhone port with USB-C, etc).
Evolution cannot do any of that, but rather is stuck with having to modify existing parts (eg, once you start with a CPU, you're stuck with it and can only improve and expand on it; once you start with a hard drive, you're stuck with it and can only improve and expand on it, etc). Also, any design mistake would be corrected by an intelligent designer, whereas evolution is stuck with it and must make the best of it (eg, the
recurrent laryngeal nerve that doesn't take the obvious direct route from the brain to the larynx but rather goes down to the heart and around the aorta, which is even worse for the long-necked like giraffes).
Common design can only account for the gross features produced,
not with how those features are designed. Instead of the same design having been implemented the same way in all products (as an intelligent designer would have done to implement common designs), all "common designs" are implemented differently because evolution is constrained to using and modifying what already exists -- a possible analogy would be that scene in
Apollo 13 where the engineers must design a repair action for the astronauts but they can only use what's in the spacecraft.
Of course, an intelligent designer can arbitrarily make whatever design decision he wants
so long as he satisfies all constraints. Every single design project has constraints, requirements of what the design must do and use.
The weird part of the creationist argument for "common design" and "intelligent design" is that what we do find with life is that it bears none of the marks of intelligent design, but rather all the marks of having evolved. So if it were "intelligently designed",
why was that Intelligent Designer constrained at all levels of the design to make it look for all the world like evolution?
I have to hit the road very shortly now, so quickly one more thing.
Those "car nested hierarchies" aren't the same as what evolution has produced because of the ability to arbitrarily change whole sections and introduced entirely new tech as described above. The ability to take very different branches and create hybrids is another; intelligent design can hybridize radically different products into something new, whereas evolution can only hybridize species that are closely related to each other, therefore no radically different products.
An example is the boom box, or the entertainment center. Phonographs, tape recorders, CD players, radios are all very different product lines with very different design histories. And yet we can hybridize them into entirely new products simply by slapping them together. Evolution could never do anything like that.
I wonder if ChatGPT could do better than the creationists on that one.
It would just do what creationists do: mindlessly parrot what they've heard other creationists mindlessly parrot.