you have pretty much the same compression as you have with a silent webm, but you don’t have to deal with audio channels and they behave more like traditional gifs, the big problem is that much like anything webp it’s not that widely supported (even a certain chat app that went through a username crisis doesn’t handle them well despite community feedback and obvious bandwith gains).

The big reason to use animated webp is where you’re in need of gif functionality but with the extra features and optimizations of modern image formats and dealing with video is straight overkill for the problem. I also don’t know how well webm deals with transparency which animated webp handles really well and is an upgrade even compared to apng.
(also gimp just handles creation of animated webp just like animated gif so even if they’re not supported everywhere they can act as a nice intermediary for image sequences if you want to have them in a single file)