Earlier quoted context omitted.
My story is similar. I've been using them for a decade, and was shopping for an upgrade when they made the proprietary drive announcmement. It was the impetus I needed to realize that it only takes an hour to build my own, better, NAS out of junk I mostly already owned and save a ton of money. I won't be going back.
You can build a little hot-swappable NAS with nice trays to slide disks in and out, an easy web GUI, front panel status lights, support for applications like surveillance cameras, etc, with junk you mostly already owned?
I think the NAS market is in for an upheaval due to the markups for fairly crappy hardware and then squeezed from the bottom by cloud storages.
RPI 5 can be got with 16gb of memory and has a PCI-E port, some might complain about the lack of ECC ram but does all those cheap ARM cpu's on lower end NAS'es really have that?
I think the biggest factor might be that case manufacturers haven't found it to be a high enough margin, but it only takes one to decide that they want to take a bite out of the enthusiast NAS market.