Google has enough moat via the Chrome, Chrome-derivative browser and Youtube client marketshare to push through a new format virtually everywhere outside the Apple ecosystem.

Yet WebP support is still pretty dreadful.

Dreadful where? In this day and age, WebP is supported by every browser, I can browse them comfortably in my file manager and basically every image-related program can open and edit them (I'm running GNOME on Arch). Where is it lacking?

I'm not a fan of WebP, mind, but the idea that support for it is dreadful is strange to me.

I think was less than a year ago that OBS got support for webp. Just about the same for Photoshop. Plenty of software still doesn’t support it or support it well. Glad your experience has been good.

Personally, the fact that it was Googles idea means I’m going to hold it at arms length, if not avoid it entirely. The web should be built on open standards.

I was using WebP-lossless for quite a few years, for the subset of images I had that fit within WebP's limitations (being the 16383×16383 dimensions and 32 bpp color depth). I've recently converted everything to JPEG XL. Old JPEGs got losslessly transformed, and both PNGs and WebP-lossless into lossless JPEG XL.

Seems to be a similar level of "works everywhere" for me, with the exception of web browsers this time.

Right, WebP was almost certainly a mistake in hindsight. Whatever advantages it had weren't worth a decade of ecosystem fragmentation. Isn't learning from mistakes and not repeating them a good thing?

I don't think AVIF is a good example of this though. All major browser makers were members of the consortium that created AVIF.

On the contrary, the webp push didn't really hurt anything... there were (IIRC) no major exploits related to it, and it sees some use. I wouldn't say it was a mistake.

But it was a tremendous amount of effort and promotion on Google's end for a relatively narrow format.

I would seriously disagree. Plenty of CMSes switched all their photos to webp resulting in a huge loss in quality.