Comment by this_user

The problem with trying to replace JPEG is that for most people it's "good enough". We already had "JPEG 2000", which would have been a step up in terms of performance, but it never saw any real adoption. Meanwhile, "JPEG XL" is at best an incremental improvement over "JPEG 2000" from the user's POV, which raises the question why people would care about this if they didn't about the previous one.