Hmm, I'm thinking about the Web-browser level (Chrome / Edge / Firefox) instead of say, web-application layer (ie: PHPbb vs XenForo).
The web browsers seems to have significantly improved compatibility of <video> in recent years, and even had decent compatibility 10 years ago (if you use Baseline profile H.264 3.0 videos and Javascript to smooth over some edges).
I've seen this debate happening for so many years, and people will not stop using gifs until other solution works exactly as a gif for the end user. APNG or WEBP would be a better solution, as they are images in the end.
You say they had decent compatibility 10 years ago, but no. At least a couple years ago you still needed many fallbacks and it was a hassle to guarantee the video would show properly. Not to say that you wouldn't be able to share it as image to tumblr/pinterest for example.
The web browsers seems to have significantly improved compatibility of <video> in recent years, and even had decent compatibility 10 years ago (if you use Baseline profile H.264 3.0 videos and Javascript to smooth over some edges).