It depends on what scale that you examine the artifacts at. At the microscopic level, there are lots of imperfections in the materials used in a car. At the atomic scale, there are no differences between artificial and natural systems.
If you take a good look at DNA you will find that it does not have unnatural symmetry or near perfection but is instead full of errors, duplications, abandoned 'code', inefficiencies and unnecessary redundancies.
Examine people engineered software code, it frequently contains abandoned (never executed) code, inefficiencies, and unnecessary redundancies. Particularly if it has been used for some time, and maintained and extended for a while.
However "people engineered software code" never looks as if it was created using a genetic algorithm (except in the rare modern cases where it *was* created using a genetic algorithm, not really "designed" in the sense you are probably reaching for, but evolved)
I have written a number of programs and at one time hacked a few games. I am quite familiar with human written code. Code maintained with as many obvious kludges as DNA does not run well, is seldom portable and is most appropriately abandoned. Programming languages have been used and abused, changed and abandoned for languages that are more efficient and encourage fewer inefficiencies. As the languages progress so does the quality of the programming. If DNA is the result of intelligent design, the designer is either incredibly lazy or an incredibly poor programmer.