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...
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)