This is web browsers developers fault: Chrome developers actively resisting APNG support [1], while Firefox developers actively resisting WebP support for years [2] and [3].
[1] https://bugs.chromium.org/p/chromium/issues/detail?id=1171
[1] https://bugs.chromium.org/p/chromium/issues/detail?id=1171
I don't use Chrome so can't be sure.
After going through the Mozilla bug threads, they're even more infuriating from a rational perspective. I guess I didn't realize how politicized software development could be, even in open source.