The bigger problem isn't that it's not user-upgradable, it's that you can't access your data in the event of a failure of any other component.

Cap blew on the motherboard? Data gone. CPU kicked the bucket? Data gone. Spilled water on it? Data gone.

Not literally gone, of course, just practically. No chance of popping the drive out and trying it elsewhere to recover data. Nope. And since Apple never repairs only replaces, you're not going to have any hope of saving your data with official repair support.

That's absolutely insane for consumer tech where backups are rare.