JXL is too new to draw any conclusions. But indeed, the market has spoken and it doesn't want avif. I tried adding avif support to a service myself, but the very slow encode speed made it unsuitable without paying for a larger server (or worse, a thumbnailner-as-a-service). Only a handful of enthusiasts (who chime in every such thread!) like avif.

Personally I fully expect jxl to succeed where avif failed and webp floundered.