I think most slowness is coming from bloated apps trying to push too much code/data over the crappy network. Additionaly it is easy to misconfigure AWS infrastructure.
And if you blindly follow that, you'll fall into exactly the trap I mentioned, where that "better architecture" involves layering another 10x+ slowdown on top of your already-slow scripting language and before you know it it's 100,000 cycles just to emit "<p>".
I think there's rather more compute-bound web-generation code out there in the world than people think, precisely because this meme makes it so people never even look. Of course you'll think it's all IO bound if you just assume it is and never check even a little bit whether that's true, which from what I can see, is the norm in the web programming world. The data can be screaming that you are in fact not IO bound, but if nobody's listening because "everybody knows" that can't be true... who's going to find out it's wrong?