Read the comment section on the article for some discussion on this. Firefox does allow users to opt-in to inaudible autoplay video blocking but it’s not the default.

The reasoning is that advertisers can approximate video with canvas tags, gifs, or just swapping out images really fast, defeating the point and needlessly burning more CPU/bandwidth. But for users that care you can still opt-in to this behavior and presumably few enough people do this that the workarounds aren’t widespread.

(The key difference seems to be that playing audio has a clear path that’s straightforward to block but “video” can be approximated by any webpage interactivity making it harder to lock down)

Would you rather websites keep using animated GIFs instead? Because I think this is why GIFs are still in active use despite being a terrible format in terms of compression/bandwidth: browsers impose all of these limitations on video, which don't apply to GIFs because they're images.

You almost can, other than the annoying animated image exception (I would really like media controls on those, you can currently only set them to play once, never, or infinitely). Privacy and Security -> under "Permissions" click settings next to autoplay -> select "Block Audio and Video" under "default for all websites".

For animated images I'm not sure if it is exposed in the UI but in about:config change image.animation_mode to "once". If you want to replay it after that, you will need to open the image in a new tab. It is somewhat easy to miss them with this setting since even images at the bottom of the page will start their single animation when you hit pagedown (even if you move the page view up again almost immediately).

Mostly this autoplay blocking has been wonderful, a massive improvement. The one slight annoyance I've noticed is that the exceptions managament isn't as flexible as uBlock origin's configuration and you can't tell Firefox to unblock all of Bandcamp. I'm not sure if this is something that could potentially be done in an addon. The other thing I'd really like is a way to default "loop" to off on media controls so that I can just play the media once by default when I do play it. Oh yeah, for some reason I can't imagine Twitter tries hard to make videos repeat and current autoplay restrictions aren't able to stop that (I don't have an account so I suspect this is a "fuck you for not making an account" thing. I can't imagine anyone putting up with that more than briefly).

There are extensions that do that.

That would result in all those videos getting replaced with gifs and wasting more resources.