As a long time ZFS user, I was excited when Canonical promised first class ZFS integration. But it was clear from the first release that Ubuntu's ZFS project was a mess. Clearly some folks got excited about ZFS, but didn't absorb much of the existing knowledge or wisdom in the ecosystem. Issues like dataset/pool layout, how snapshots were handled on update, were handled in completely unusual and boneheaded ways.
The ecosystem already had the concept of boot environments, which more or less standardized what a rool-on-zpool layout ought to look like, and how to handle graceful, recoverable system upgrades. What Ubuntu could have brought to the table was a really high quality beadm replacement for Linux, moving Grub's ZFS support forward with support for more feature flags and boot environments, or investing in ZFSBootMenu.
Instead they went ahead with zsys, and it's still not entirely clear what they want or expect it to be. That they needed to write a daemon to enable "complex zfs dataset layouts" should've been an early clue that they were going down the wrong path. The dataset layout for a root filesystem should never be so complex, that you need to write a whole daemon to manage it.
The packaging issues and bad patches are almost besides the point.