@kornel I got lost in all those "soon to be popular" image formats.
We had GIF, JPEG, PNG in past (still have). Then WebP arrived and took some time before it became some kind of popularity.
In meantime there was JPEG2000, JPEGXL and probably few other mutations which were mentioned as "soon".
And <imgset> tag was announced as a solution for web devs. To provide jpeg2000, jpegxl, webp, jpeg etc images in hope that browser will choose what they support. Or this is how I understood it.
@hrw The old JPEG is exceptionally good, like alien technology from the future.
Also interoperability is more important than anything else. People care more that the files will work everywhere than about file size savings (GIF is an extreme example of this).
JPEG XL is a very complex format, because it's trying to beat every other format at everything.