Example post: https://cohost.org/atomicthumbs/post/902461-discusting
The first image has a roughly 3:1 aspect ratio, which is being fit into a square-ish hole. The client cuts off the edges and centers it. But the height of the hole isn't sent, so the image gets shrunk way down to fit to width, and then scaled back up and is impossible to read.
(Did some messing around and it seems adding a height= parameter along with fit=cover does what I'd expect of an image optimizer for this use case.)