TL:DW, JPEG is getting old in the tooth, which prompted the creation of JPEG XL, which is a fairly future-proof new compression standard that can compress images to the same file size or smaller than regular JPEG while having massively higher quality.
However, JPEG XL support was removed from Google Chrome based browsers in favor of AVIF, a standalone image compression derived from the AV1 video compression codec that is decidedly not future-proof, having some hard-coded limitations, as well as missing some very nice to have features that JPEG XL offers such as progressive image loading and lower hardware requirements. The result of this is that JPEG XL adoption will be severely hamstrung by Google’s decision, which is ultimately pretty lame.
Pretty much sums it up. JPEGXL could've been the standard by now if Google would stop kneecapping it in favor of its own tech, now we're stuck in an awkward position where neither of them are getting as much traction because nobody can decide on which to focus on.
Also, while Safari does support AVIF, there are some features it doesn't support like moving images, so we have to wait on that too... AVIF isn't bad, but it doesn't matter if it takes another 5+ years to get global support for a new image format...
People are quick to blame Google for the slow uptake of Jpeg XL, but I don't think that can be the whole story. Lots of other vendors, including non-commercial free software projects, have also been slow to support it. Gimp for example still only supports it via a plugin.
But if it's not just a matter of Google being assholes, what's the actual issue with Jpeg XL uptake? No clue, does anyone know?