https://caniuse.com/#search=webm

Also, nobody seems to make use of these features, but GIFs do not have to loop, nor do they have to loop by going back to the very beginning of the animation as well. In particular, I find it extremely ineffective where there are GIFs that only show a "final product/scene" for like 1 frame before looping back to the beginning.

I don't think that's true.

Twitter and imgur do convert gifs to mp4, and you can see controls there, but that's because they're not gifs.

Do you have a citation or example of controls on actual gifs in any commonly used web browser?