Indeed, a machine is a machine, regardless of complexity. And even that is probably too specific: a product is a product. Either it needs to change, or it doesn't need to. And the layman cannot tell the difference from looks alone.
There may be very good reasons why a paperclip doesn't need to evolve but the key to your door absolutely must; why the bicycle is just fine the way it is but the roller skate was shit before it got better; why the hull of a dry cargo vessel from a hundred years back is fine but the hull of a container ship from ten years back is hopelessly outdated for meeting the current demands of most economic movement through water; and why a howlizer from WWI would still serve while a cannon would be useless. Sometimes the reasons can be found by googling, sometimes not. With starships, we can but guess.
It isn't even a metaphor. It's more like a universal law of nature. Except you replace nature with the artifacts of civilization, and insert intelligent design where nature has none.