HN user
kitty is much better than the rest on latency, see hardware based measurements https://thume.ca/2020/05/20/making-a-latency-tester/
showing kitty has the same latency as terminal.app on macos.
It has, just not fully. See the very first checkbox in the link you posted. Indeed this protocol is designed so applications can pick and choose what parts they want to use.
The progress is that this protocol has been implemented in many widely used programs, such as vim, neovim, helix, kakoune as well as at least two more terminal emulators, wezterm and foot in addition to kitty.