I like the XDG specs, but even programs that pretend to follow it don't follow it. CMUS, a music player, moved into ~/.config.. moved everything, including files that belong to .cache and .local/state. Google Chrome has 999 mb worth of files in its .config folder on my computer. The truth of the matter is that XDG only managed to encourage developers to move their files away from the root of $HOME but they didn't manage to make people respect a proper hierarchy of files.
This is a great point, honestly. XDG actually does specify where things are supposed to go, and distinguishes between config, cache, state, and strictly-user files, but devs don't respect that hierarchy, either.
I completely fail to understand this viewpoint. The non-config files that I intentionally put into $HOME are infinitely more valuable than anything I would want to backup from .config.
I have hundreds of gigabytes in non-hidden sub-directories of $HOME, such as all my family photos, all my health-related documents, all my email, and so on -- and they are backed-up every single day.
Why is backing up your actual files in $HOME a non-starter? What makes your .config more valuable than everything else in your $HOME?
If only the last stubborn applications would comply, I would have just 1 place to look for config, and one place to wipe caches.