This is a chicken and egg problem. What is Mozilla's incentive in spending any effort on JPEG XL if Chrome doesn't support it? There won't be any demand for it from content creators until the majority browser adopts it.

The only way to protect the web users' interests against Google's commercial interests is to dethrone Chrome - no matter how farfetched that sounds. It's such a shame that the world managed to paint itself into a corner again inspite of the bitter experience with the earlier browser wars.

Mozilla has stated that they will support it as soon as a memory safe decoder is available. If Chrome doesn't support it then, it's reasonable to have this discussion.