I did and do understand file trees and how to navigate them, and I think they aren't good. They are a carryover from the physical world of "a place for everything and everything in its place" which means you need to remember which room and cupboard and shelf everything is, go there, open the cupboard, and get it.
In a computer, it can be "anything you want appears wherever you are, when you need it". This is hugely more convenient. Let the computer deal with storage (and versioning) similar to garbage collection dealing with memory management. Locate on Linux and VoidTools Everything on Windows let you conjour things up without caring where they were stored, and increasingly photo libraries let you search by the content of pictures rather than the filename. Full-text search is also imaginable although on Windows it's not been good enough to use for years.
The idea that the ever-growing list of things I use a computer for should take an ever-growing amount of space in my head to remember where everything is, is a bad idea. "Everything" tells me my comptuer has roughly 1.4 million files; most of them were put there by installers, not directly by me. If I can not-care about the location and storage of ~99% of them, why can't I not-care about the storage arrangement of 100% of them?