This is a really poor excuse. Just because you're technical doesn't mean you're not responsible for presenting your content in a appealing and clean way.
beauty is in the eye of the beholder. A diagram that conveys the information that took the minimum amount of time to generate and has the aesthetic that appeals to the engineer is beautiful. Maybe you have different taste?
Point was, you're not likely to get a purely functional resource out of marketing, not whether engineers are capable of producing marketing-quality materials.
*edit: shitty as in pixelated; not the content