My understanding is that JPEG2000 never really demonstrated, in experiment, that it was better than JPEG at the types of images and use cases which JPEG was alr

My understanding is that JPEG2000 never really demonstrated, in experiment, that it was better than JPEG at the types of images and use cases which JPEG was already designed for (photographic images, lossy compression). This use case is such a dominant use case for the web. If you wanted similar quality levels for JPEG and JPEG2000, you often got similar file sizes. I could dig up some of the tests, but the basic gist of it is that at lower file sizes, JPEG2000 would get blurry and JPEG would get that funky blocky noise it gets. This is the result of actual experiments with human subjects judging image quality. I haven't really heard claims that JPEG2000 is better, actually. I remember people saying that it was "supposed" to be better, but not by people who dug into it and made comparisons with human eyeballs. There were some images that would appear visibly better with JPEG2000, like photographs with those beautiful fields of defocused color. JPEG2000 captured those fields of color with all the smoothness they originally had.