I've tried pretty hard to get it to work with ffmpeg and mediaRecorder, but both of these options are quite limited at the moment and the results just weren't good enough. Other option would be to go server-side which I don't want to do.

I was unaware the rendering could and was being done client-side! Given the limitations I can see why gif would indeed be suitable format. You've tooled a compelling amount of functionality into something very lightweight and convenient, and that's a more than acceptable tradeoff.

Your opinion is misconstrued.

How? Of course asking OP to add features for a site he offers for free is wrong, but I don't think he's wrong about gif. As far as I know all the "gif" sharing sites like giphy and stickers in chat apps like discord, etc actually use webms/webps.

Gif is simply the most versatile format on the face of the planet. When you go down the rabbit hole you’ll discover this too.

Twitter for instance automatically converts gif to h264.

However there is a point to be made that iOS only grants VP9 decoding to Youtube, certain colourspaces fail to decode on Android etc. ergo gif is a safe default.