I think the triviality and inadequacy are overstatements for the following two reasons: it's rare to have undetected errors in normally operating hardware that simultaneously go undetected by Btrfs. If this doesn't go far enough, then I'm challenged how to characterize the vast majority of the world's data on NTFS, HFS+, ext234, and XFS as being anything but fragile and tenuous, which would be an overstatement. What is going far enough? It's a use case question rather than something absolutely determinable. For a general purpose filesystem, I think CRC-32C is adequate, although it will be nice when there's choice for another algorithm to meet other use case requirements.

Yes, it won't send writable snapshots. e.g. ERROR: /mnt/root is not read-only.