"think you've read too many horror stories about unreliability of flash memory..."

Given my collection of dozens of dead SSDs I have my own horror stories, my comments are based on painful experience.

In most instances whenever I've had a HDD fail—and that's many over the years—I have been able to recover the data but I cannot say that about SSDs or USB thumb drives as they mostly fail catastrophically and without warning—and the data is irrecoverable. Moreover, with SSDs, in cases where data has been accidentally erased, wear leveling often mitigates against successful recovery.

I've lost far more data to SSDs than I ever have to HDDs yet I've only been using them for about one third as long. I've now reached the point where I don't bother to recover data from a dead SSD as I know it'll likely be a futile effort. That's still not so with HDDs but there are exceptions.

Moreover, whether it's hardware failure or accidental data erasure, ALL SSD and USB thumb drive manufacturers either provide no recovery tools or if they do then they are inadequate almost to the point of being useless (for instance, SanDisk's recovery tool is hopeless, I've just unsuccessfully tried it on its own 256GB SD cards). My contention is that if the firmware architectures of these devices were actually designed to be aware of file structures then recovery would be easier. Essentially, they're still not user-friendly and manufacturers have made little or no effort to rectify the problems.

"SSD firmware is a pile of overcomplicated software developed in a hurry and squeezed into an embedded system with limited resources."

Limited resources, why? A 500GB SSD is orders of magnitude larger than even the most bloated firmware would occupy. (The world' most bloated software Windows only takes about 7GB!) If SSD firmware is developed in such a hurry and thus jeopardizes users' data then I would contend the products are not fit for purpose. The fact remains that SSDs are intentionally made as 'black boxes' by their manufacturers and I'd maintain that this is highly unsatisfactory as far as users are concerned.

We ought to be long past the point where users' data are put at risk by shoddy or limited design efforts and or the desire of manufacturers to keep their designs secret. Nowadays there's too much at stake just to hold the world's data inside black boxes that no one understands—ones that not even manufacturers can recover (or are willing to recover) data from when they fail. We users deserve much better. [In saying that I'm no apologist for HDD manufacturers who adopt similar tactics.]

"A NAND flash memory chip is a massive array of highly-regular memory cells that have been thoroughly characterized both in terms of aggregate/average behavior and localized defect rates."

First, your point about SSD firmware complexity. Perhaps you are correct but I'd not be convinced until seeing the architecture and source code (it's not only SSDs, where the secrecy/lack of source code is a problem, it's a serious issue with many products and likely won't be resolved until AI is usefully deployed into reverse engineering it.)

Clearly, you have considerably more faith in NAND technology than I do. That's fine, your objectives are likely very different to mine. I'll just say this, current tends in NAND technology where more and more bits are stored in smaller and smaller 'cells' crammed in more and more stacked layers and that each data bit consists of fewer and fewer bottled-up charges that eventually leak away despite quantum potentials trying to keep them in place, is not my idea of a reliable, permanent storage system.

I've been recovering data from dead drives of both types for quite some time now so my views are mitigated by how difficult it can be. I'm not defending HDDs either except to say that as a more mature tech and given its storage architecture it is easier to do so. I'll also grant that recovering data from some HDDs is intractable but such instances are comparatively rare.

Incidentally, I remember one such failure very well as it was so obviously connected with what I did. It was a Connor Peripherals 20MB drive—yes, it was a long while ago—in a desktop PC. I dropped a small book onto the table where the PC was and the drive instantly gave read errors. Despite strenuous efforts, its data was irrecoverable.