Tags are far superior to hierarchy, yes, because hierarchy is inherently single-path. (Ironically, I added tags to the emacs-based mailer I was using at the time in the mid-80s for exactly that reason: I needed to be able to apply more than one tag to a message.) But until operating systems catch up and give us a lightweight and portable way to tag files, directories are what we have. (It does me no good at all if MacOS has "labels" -- not sure if those work like tags -- if those labels won't follow the file to Linux or Windows.)

I just had this problem with the blog software I'm setting up: URLs were all of the form "blog/entry-title", but I wanted "blog/2021/entry-title" or even "blog/2021/10/entry-title" because, you know, I might want to talk about Yom Kippur in more than one year and I might reach for the obvious name. Without hierarchy I'd have to add temporal tagging, so that an entry might be tagged "Judaism" and "2021" and the combination of all tags + file name would need to be unique. I think I would find that hard to manage if I couldn't actually use hierarchy for the temporal axis, but maybe I'd get used to it. (I did sort out my URL problem.)