Earlier quoted context omitted.
I absolutely agree with this, except to add that it seems, in theory, in the case of a 100% tag-based file-system, there would never (*very rarely) be a flat list where you have to scroll through millions of files. The UX of a single flat list with millions of files named DCIMxxxx.jpg is a limitation of the current format and doesn't make sense when so much information can be generated about our files upon creation.…
Part of the adoption problem here would be trust. Hierarchical filesystems are something we're used to, and we can trust they're implemented correctly. That means, if I visit a folder and see some files, I know what I see is all of the files there (+/- hidden file settings); if something is missing, it's not there, period. Tag search is a search. Can be broken. Can be optimized in a way that causes it to lie. I look…
Google Docs, while not exactly a tag system, wants you to search instead of use a hierarchy, and so is my go-to example: A good 90+% of the time, I can't find something I know is there and have to ask a co-worker for a link.
The missing consideration when it comes to tags is simple discoverability. You have to already know enough about what you're looking for in order to find it. A hierarchical system lets you do systematic browsing.