That post was written by a designer judging designs.
His attention is biased by the practice of seeing and understanding dozens of visual languages. But he doesn't understand that, unlike a painting, a poster isn't the purpose, the end. A painting in a museum exists for itself. A poster in a street exists at the service of a commercial message. The poster isn't the focus or the point, the message is.
He looks for visual languages, but most people would look just for information: what, who, where, when, why. If they need to spend more than a tenth of a second to decode the visual language of a poster then the poster failed.
There is a famous book on UI design whose title defines very well the design principle for things that should face the masses: "Don't make me think".
As a designer, the post author seeks the unexpected. Normal people just overlook and avoid it.
Normal people love the bland and repetitive precisely because it is familiar. That's the reason there are so many more McDonald's and similar franchise chains than fine French/Italian bistros and unique shops. That's why people listen to dumb pop and country music but not Stravinsky. That's why so many people watch Hallmark movies. People choose boredom because that's something they can easily understand.
Peopel are dumb, they don't want to think.