What do mean? It's used pretty extensively.
What people call GIFs these days are almost always not actually GIFs. GIFs will usually have high dithering due to it using an 8-bit color palette and an odd frame rate because the per-frame delay is specified in jiffies so you can't really get normal framerates (especially high ones).
What dethroned GIFs was the <video>
HTML element. The video format doesn't matter.