Apps dumping cache/state into ~/.config/myapp/ is still better than ~/.myapp in the vast majority of situations. I can still usually afford to sync / strongly back up ~/.config even with a few bad apples barfing heavyweight cache/data there (and I can always use ignore rules), while syncing all of $HOME is just a nonstarter.
> I can still usually afford to [backup huge caches incorrectly placed into ~/.config], while syncing all of $HOME is just a nonstarter.
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?