Author here: as I wrote in the piece, I've recently dumped Photoshop for Pixelmator Pro. It doesn't currently support AVIF. Photoshop does, but not in a way that makes it easy to optimize an image for web export. JPEG XL is also exciting to me, but it's not generally available across browsers. WebP is the current best image format for my use-case, but I'm hoping others supplant it soon.
reply>but it's not generally available across browsers.
replyNote that this is changing rapidly. Safari ships JXL, Chrome did a few days ago, and Firefox will in the next few days. Once this flows through to all the chromium based browsers we will see pretty much 100% support on the web.