"Slop" is not determined by quality, but by intent. If no one responsible for making it cares about the quality of the output, it's slop, regardless of how well-made it might be; on the flip side, even if something is really bad, it isn't slop if the people making it are really passionate about doing the best they can. Kurzgesagt might be low quality, and it might be slop, but the two are not necessarily dependent upon one another.