While I am firmly in the ZFS camp, my feeling is that there has indeed been a gradual slide in the disciplined development of ZFS.

After some initial bumps in brand new software, the Sun kernel group did a good job of avoiding corruption. Once Sun was absorbed by Oracle, OSS ZFS moved into illumos, who were overall quite good at doing the same (although they had less resources to play with). OpenZFS brought ZFS to the rest of the world (good), but I can't help but notice that the illumos devs are increasingly worried about pulling changes back from OpenZFS into illumos.

The increased popularity is for the best, but the change rate has increased, with all that entails.