I think there's clearly a strong "point of view," but whether or not there's an actual argument seems to be somewhat unclear to me.

"Flat design happened! Then homogenization happened!"

Ok, that seems to be more or less true, and yes, homogenization is bad. Everything looking the same is what really depresses me as a designer in the current climate. As others here have noted, however, flat UIs are ubiquitous because there are a lot of designers in the world producing flat UIs. Why are they doing this? A mix of influences, some from the likes of Apple and Google, but some from end users themselves. To the extent that flat principles assist users, why are we so willing to rag on them?

I feel like the article would be stronger if:

1) An actual case for some trend other than flat design (yes, they're all trends) were made. It sounds a lot like this particular designer feels like his personal style is under attack and is bitter about it. The examples given are, I think, useful, but they don't speak to all instances or to why a design trend on the macro scale is better than another one.

2) The case were presented in terms of what is most helpful to users instead of what is most desirable for designers.

3) The possibility that there can be differentiation within flat design were entertained. Not all flat web UIs need to be "blurred hero with centered text." Not all Twitter apps need to look the same. Maybe this new kind of differentiation looks exactly like the "dimensional" example Eli presented. Flat design can be balanced with other aesthetics. It's not antithetical to them, or at least it shouldn't be.

Anyway, I dunno. I would never write a post like this on my own blog because it seems to be so anti-user in both tone and sentiment. It seems to be "all about us," the designers. And maybe this is the artistry part of our work taking over for a minute and supplanting the problem solver part. Perhaps we want to keep a hold of our creative visions. Heaven knows I've gotten sick and tired of designing flat UIs for clients within the "visual monoculture" of contemporary design. However, I'm still puzzled about what the alternative should be in the context of our responsive world.