One, Red Hat is one of the major contributors to XDG, and is pulling developers away from XDG projects. To what extent I am not fully aware. We've learned time and time again that for-profit entities should not be in charge, or highly influential, in standards. They will inevitably steer them to favor their own ideas.
Two, what luck has the greater community had in getting their ideas adopted to the 'standards'? Standards are not meant to be inflicted; if a standard cannot gain enough consensus, and lacks authority to control who publishes software to a platform, then what good is it? XDG comes from the GNOME and KDE crowd, meaning Red Hat/IBM, Trolltech, and maybe Canonical or a few other token companies. Notice the complete lack of real community input or control? If I wanted to defer to a standards body, I wouldn't be interested in software. I don't think software is about bending to the will of some third party group's idea of how computing should be done.
Three, kind of a nitpick, but they adopted the Contributor Covenant CoC which is problematic for people who respect compartmentalization of social spheres. I don't care if there's a dipshit bigot on a dev team as long as he or she keeps it out of the work environment.
I have sidestepped the issue (in my mind) by putting all personal files in a `~/me` subdirectory, and create symlinks in `$HOME` to point to the relevant files in `$HOME/me`. It keeps things separate, and anything that's put inside an XDG folder that I want to hold onto can be migrated to ~/me and symlinked. I keep a short bash script that I use to (re)create the symlinks for me, as needed.
A distro that feels really strongly about XDG could patch, or refuse to package anything that doesn't adhere to XDG. I wonder how far that approach would go.
In short, I am just not impressed with the way XDG is handled, nor the literature that gets pushy about people adopting it. The author used a sleight of hand to imply that XDG is an authoritative standard or that it has universal consensus. It is not, and does not. This dishonest representation of the XDG standards are part of why I am turned off by them. It's the same social approach that PulseAudio and systemd used.
If things are good, they will be adopted on their own without any advocacy needed.
(Edit: added third concern after checking their site more)