I've definitely heard of "goat" as a noun meaning that, but "webp is such a goated format" sounds more to me like the writer thinks people try to laud it as the goat when it actually isn't. I guess it's because it sounds like the passive voice; "is goated" makes it sound like someone else is doing the goat-ing, at which point for something subjective and desired like "goat", "goating" sounds like it's being used as a more modern slang for "astroturfing" or something.

One of the car rental companies has started using it in their commercials. I do wonder how much of a generational divide there is on using it.

Have not seen it in common use. I think most non-native English speakers will associate with it being an ugly format.

Well then it should be "a goat format" instead of goated...