I think we have all the tech needed already (WebRTC, DHT, NAT hole punching, decades of p2p, encryption, onion security, StorJ/Filecoin) etc but what is lacking is dead simple UX and wide support of operating systems - Windows, Mac, Android, iOS, Linux (Raspberry, Synology, cheap VPS backup)
I'm still waiting for a 'Drobo' like device without the proprietary physical layout. A light or dial goes into orange territory, you head to Best Buy or Amazon and buy the biggest drive that doesn't give you sticker shock, you push a button, out pops your worst drive and in goes the new one. Some lights flicker for a while and then go green.
I thought ZFS would have given us almost everything but the hardware ten years ago, but it turned out they oversold a few of the features back then, and then Larry happened.
Custom hardware is too expensive for small run consumer hardware, and Apple might have gotten into that space but never did. I wonder how many PCIe lanes you could shoehorn onto a Pi clone...
A freenas box does this as well, but won't have the pretty drive light indicator if it's a home-built box, but then you're not limited to proprietary hardware.
For the physical device at least, Debian and 2 Btrfs data drives in RAID 1 certainly isn't turnkey but seems quite accessible at this point.
Still looking for the perfect Dropbox-like experience but without the cloud sync piece. If only syncthing had decent mobile apps...
The only major drawback seems to be that you have to host the physical hardware yourself due to lack of solid end-to-end encryption for most platforms. Sandstorm might have it (I'm not clear on what's client- and what's server- side there), Seafile has end-to-end encryption that doesn't protect metadata (https://forum.seafile.com/t/how-strong-is-the-encryption/627...), and NextCloud appears to have a long-running beta of end-to-end encryption on a per-folder basis (https://nextcloud.com/endtoend/). Apparently Cryptomator exists (https://cryptomator.org/) although I've never tried it myself.
If you want to decentralize your shared files unfortunately last I checked SyncThing didn't yet support end-to-end encryption. (I don't think any of the other ones I mentioned can be used in a decentralized manner but things move quickly so I'm not sure.)
Alternatively, if you were thinking more chat and messaging there's self hostable federated services such as PixelFed, PeerTube, Mastodon, and Matrix. Or was there some other usecase you had in mind?
I'm looking into integrating with DAT or Hyperdrive-like solutions to help make storage backups less fiddly for users.
For now, I recommend my beta users use SyncThing or Resilio Sync to get their photos and videos off their phones and on to their home NAS or computer.