My competing definition includes safety and performance. Not about how the system works a single epsilon after an operation but perhaps reading data that we wrote last month, or last year and doing it using the hardware's resources efficiently.

Clearly either your or the ext[234] developers are mistaken as they have gone ahead and implemented extent based allocation and file management.

btrfs's design is inherently safe while ext2's design is inherently unsafe. To make the analogy work, I would say that ext2 does not fit the design spec for a file system; it would be like a garbage collector that does not actually collect garbage.

The payout for data integrity, which no filesystems really handled until the WAFL era, is huge. If you cannot see, this discussion has no point.

The only thing that I must be honest about is that I would not trust ext2 to store my data any more than I would trust you to implement a scheme to store my data.