The nature of preference-ranking in LLM post training means that "slop" is something that the average person actually prefers. Maybe there's an argument that it's not intentional but just emerges as a form of reward-hacking (e.g. people like a little bit of slop or sycophancy but the model dials it to 11) but I imagine if the end result wasn't rewarded ultimately that would get penalized.

The fact that a clearly sloptacular image won first place seems to corroborate that indeed people do like it. Until people's tastes change and they learn to recognize and immunize themselves against slop, the models will continue to generate it.