In defence of the guacamole-eaters...
I'm a developer with 20 years' of experience, and this just isn't true. I can use Photoshop/Illustrator/Gimp with the best of 'em, but I'd never call myself a designer.
I thought I was, when I was young and foolish. Now I've worked with professional designers I realise that all I can do, from a frontend point of view, is stack the blocks.
Good design is a real skill that takes years to attain. Sure there are some useless crayon-wielders out there, but a good designer would have asked your question before anyone else did. And they'd have kept asking it in different ways until they got a working design.
Or perhaps I've just been lucky in my colleagues.