(In reply to Jan Andre Ikenmeyer [:darkspirit] from comment #2)
PIK looks terrible compared to WebP and AVIF.
True for low bpp. However, wyohknott.github.io is comparing an outdated (perhaps 1.5 years old) version of jpeg xl, and should not be used for making actual comparisons.
JPEG XL's candidate lossy encoding from last summer performed well at 1.0 BPP and above. We have recently made it perform competitively down to 0.25 BPP. For some classes of images (particularly portraits and natural images) it is the technology leader at low BPP with a margin. For some other classes, such as screenshots, it is still not competitive.
Also, we made the default mode about 10x faster in compression, and greatly improved the quality of the fast mode.
Currently we are in the process to integrating FUIF and PIK in a useful way and deploying a couple of additional significant quality improvements.