GIF only has binary transparency. Period. Also GIF is only lossless if you don't care about file size (using multiple 0 duration frames with different palettes trick) or material is limited in palette.
From my testing VP9 videos with transparency are fine if you aren't stingy with bitrate, and in general if source material isn't CGI things will be crusty at edges anyway (e.g. greenscreen with motion blur).
You get 256 colors per frame. Want more colors? Use more frames! There's some really impressive software/gifs at https://gif.ski/ if you want to see just how far it's possible to push this terrible format.
From my testing VP9 videos with transparency are fine if you aren't stingy with bitrate, and in general if source material isn't CGI things will be crusty at edges anyway (e.g. greenscreen with motion blur).