“If you want to see the future of software UI design, look to the history of print design.”
After some thought, I’ve decided that I agree with John Gruber and Dave Wiskus, but not for the same reasons. I don’t think Retina displays have much to do with it at all — in fact, Retina displays are even better at displaying subtle textures, lighting and shadows. Those extra pixels go a long way in providing additional suspension of disbelief for realistic user interfaces.
Like many trends in technical areas, interaction design is being led by technical ability.
8bit games looked 8bit-y, because of limited colour palettes and giant pixels. 16bit games looked 16bit-y because of better colour abilities and slightly smaller pixels than their 8bit counterparts. Newer games look newer, because GPU hardware developed to the point where full 3D games were possible. These aren’t stylistic choices, they’re hardware limitations, dictating how software looks.
In the same respect, print design has limitations to work with. Most body copy in print design is black, because of hardware abilities — black is one of the four printing plates, so it can be reproduced at high quality, with sharp, fine lines needed for text. Back off a little to a mid-grey and the quality drops significantly, because you’re still using black to print, but you’re building mid-grey from a dither pattern of small black dots on white paper. It’s a trick. There is no mid-grey, only black or white. And because of this, smallish text printed as mid-grey looks horrible (please note that I’m talking about typical four colour CMYK offset printing, not the use of special colours).
Some gradients in print design are hard to reproduce. Subtle edge lighting effects are a often disaster, due to press registration (alignment of the colour plates). Shadows against the paper colour almost never look good, because very light colours are hard to print, so there’s typically a hard edge at the light end of the shadow, cutting it abruptly. Some colour combinations are a disaster to trap.
Print design looks like print design, because there is no other choice.
And just like print, I believe that all non-iOS platforms have settled on mostly-flat interfaces due to technical constraints. Both Android and Windows 8 target many display sizes, ratios and pixel densities. Android also targets incredibly low end hardware, as well as high end hardware. These factors are vital when critiquing platform design choices.
In interface design, square finished corners are faster, because there’s no masking. Not including shadows is faster, because there’s less compositing. Drawing a flat colour is faster than drawing a gradient. When you have three or six pixel densities, drawing sharp textures is almost impossible, unless you include bitmap assets for every size you’re targeting.
iOS is like iOS, because it can be. Because the hardware is so tightly linked to the software.
I love Letterpress and I do think its interface is both modern and good-looking. I also love The Incident, in all its 8bit glory. And I love Clear. I love many flat-design apps. But I also think we’re only one “holy shit, that’s a user interface?!” moment away from the next pendulum swing back in favour of realism. Chances are that app will be on iOS.
So, yes, the future of UI design will be like print design — marred by technical constraints, resulting in certain style choices being popular.