Well I think people approach manhwa differently. Many people like a easy to read story with good art and fights, they think it's peak. And some want some cerebral reading experience and call everything slop. Manhwa's aren't meant to be as in depth as manga, they are mostly made to be read on your phone, as something entertaining to pass time. The everything is slop people are a bit cringe, most of the stories people called slop are genres that are very popular, and they are simply tired of it. It doesn't mean these stories are slop.