You can totally spend a lot of time making sure stuff is categorized in the right folders. Anyone who has had an illicit mp3 collection has probably spent a ton of time doing just that. However, that's less relevant today, and for documents and pictures, I can basically just chuck them in a folder then search by date, location, or even person in them without a ton of effort. Full text searches are fast at the "these are my documents" scale, and the price of storage is cheaper than a nice meal at a restaurant per year.
I'm able to keep almost everything, store it for pennies a week, find what I want instantly, and spend almost no time doing any of that. I feel like going through a decluttering would spark less joy than tossing everything into a folder and going on with my life.
So what if I ever need that scanned PDF from 2007's taxes - finding and deleting it would take more effort than just leaving it on my NAS...
OR... maybe... you just haven't found an app that can gracefully clean up your mess yet.
I can't help with general documents, but for photos and videos, I wrote PhotoStructure to tidy up my family's digital disarray. It's runs everywhere, libraries are cross-platform and cross-machine, it imports almost all image and video formats, has robust image and video de-duplication, and at least for the next couple weeks, is still free to use during the beta, in exchange for your feedback. https://photostructure.com/faq/why-photostructure/
> Here, digital hoarders are characterized by laziness or a general lack of organization. Data accumulates over time and without active management habits a disengaged hoarder can accidentally end up with a mess of digital clutter.
What's the harm of having nested "old PC junk" folders containing everything on every PC I've ever owned? Storage technology has continued to progress, so it doesn't cause any problems, and it's kinda out of sight, out of mind.
I think it's a mistake to apply a word with negative connotations like "hoard" to behavior that doesn't actually cause any problems (except ironically as in /r/DataHoarder).
I have two Synology devices, one at home, one at my parents' place as an offsite mirror. I use both Dropbox and a self-hosted Seafile. Instead of deleting stuff I just trust that soon I'll have more than twice the storage for less than I paid last time. And since I got into tinkering with Raspberry Pis and Arduinos, I've also been recording gigabytes of environmental and personal data in case I want to "mine" it some day.
Maybe I do have a problem...