WebM is just a container format, though it's usually used with VP9 and opus, and is functionally equivalent to using any other kind of actual video.

Animated GIFs remain quite useful for non-video animations where you don't want lossy compression, and want to use other GIF features like transparency. Animated PNGs are a potential replacement, and support all of the features of GIFs along with 24-bit color, but software support remains lackluster.