It's better WebP, without patents and license fees (so unlike HEIC). There are also advantages to encode and decode speeds compared to other formats. It's a superior format compared to most alternatives in many situations.
Adding the format and maintaining it requires some work, but the potential for load speeds and data savings is huge. It's also finally a somewhat efficient format for bitmap animations after all these years of GIF and APNG. I've also run into the 16k size limit while converting some PNGs to WebP myself, to JPEG XL would be a nice way to losslessly compress those images more efficiently as well.
That said, so far WebP is serving me fine in most cases, I don't really care if it takes two weeks or two years for JPEG XL to make it into the mainstream.
It doesn't matter that it's better than WebP, because that isn't the alternative. The alternative that browsers have shipped is AVIF. JPEG XL's advantage over AVIF is less significant. It's not a clear win, but diminishing returns and nice-to-have features vs AVIF's wider deployment and head start in AV1 implementations.
Adding the format and maintaining it requires some work, but the potential for load speeds and data savings is huge. It's also finally a somewhat efficient format for bitmap animations after all these years of GIF and APNG. I've also run into the 16k size limit while converting some PNGs to WebP myself, to JPEG XL would be a nice way to losslessly compress those images more efficiently as well.
That said, so far WebP is serving me fine in most cases, I don't really care if it takes two weeks or two years for JPEG XL to make it into the mainstream.