Seems to me like people are agonising over skeuomorphic details as basic as using drop shadows and gradients to make a button look 'real'.

In recent months I've come to realise that (excluding so-called 'flat' design) such processes have sublimated and that we have actually converged on a new visual language for communicating a control's affordance.

Let's look at the basic button: we no longer make a button look like a button, per se, so much as we simply add contrast to the control's edges (according to taste), and perhaps overlay a low frequency over the entire control (otherwise known as a 'gradient').

Then, when a user activates the control, we rotate the phase of the control's spatial frequencies through 180º to communicate its state (equivalent to reversing all shadows and flipping the gradient).

I think flat design sucks because it effectively excludes you from using visual frequencies this way - it's a bit like asking someone to record a song, but they have to run everything through an extreme high-pass filter, or a bitcrush, or something (I dunno, someone help me out with this metaphor here).