This is largely a myth, please provide an namespace-related CVE that has gone unpatched to support your argument. The reason they run as VMs is that hypervisors run on ring 0 and require higher privileges than the kernel, therefore they are naturally more secure. Like Namespaces, Zones and Jails are also managed by their respective kernels. If there were any major hosters running managed services for Zones and Jails, you can bet they would implement them in a similar way.
> Due to CDDL and GPL problems ZFS on Linux will always be hard to use making every update cycle like playing Russian roulette.
You're right in that the CDDL causes complication but I don't consider this to be a compelling reason to use Illumos. Many who want to use ZFS on Linux will use it and get it to work despite the licensing issues and complications.
> Like SMF offers nice service management while not providing half an operating system like systemd.
SMF is relatively nice (apart from the use of XML) and like you, I would not touch systemd barge pole. Despite systemd making a lot noise in major distros, there are plenty alternative distros for those of us who don't want to use it.
Don't get me wrong, I'm a Solaris guy, it made my career. I just fear that by dropping SPARC, Illumos have put the final nail in their own coffin.