Earlier quoted context omitted.
Author here. That is good criticism! Thanks for bringing it up. I didn't consider other factors like ease of sharing. They are definitely tradeoffs. At least for my personal website, the size disadvantage of GIFs still outweighs them, in my opinion. I think bandwidth usage and battery drainage are also worth thinking about on behalf of the user.
The irony is a modern gif filetype would be even better. Something that retained the advantages of gifs, but allowed for better compression.
I mean, I know everybody is really pumped about webGL and shadow DOMs and webcomponents and webASM, but I feel like the basic "html as document language" could use some loving to solve this.
This whole mess reminds me of SVG. I get that there are fantastic reasons why SVG has JavaScript and its own DOM and can pull in external resources, but sometimes we don't want a whole new framework for new forms of content, we just want an IMG.