Note though that unlike zfs, ext4 has a battle-tested fsck.

Combine ext4's dumb but robust approach to journaling and robust metadata layout (for example inodes are statically allocated) with fsck.ext4 (which got refined for years) and you can recover from any situation.

To give you an example, fsck.ext4 will happily carve a working filesystem out of random data, as long as there is a valid superblock. Seriously - try it yourself:

  # create a working filesystem image
  dd if=/dev/zero of=test1.img bs=1M count=256
  /sbin/mkfs.ext4 test1.img
  # write file with random data
  dd if=/dev/urandom of=test2.img bs=1M count=256
  # copy superblock into random file
  dd if=test1.img of=test2.img bs=1024 count=4 seek=1 skip=1 conv=notrunc
  /sbin/fsck.ext4 -fy test2.img
  sudo mount test2.img /mnt/somewhere