Maybe it's just me, but perhaps I like the company who actually wrote the scheduler powering the service you mentioned, has run it in production for over a decade and gathered petabytes of knowledge about how to refine it, has been working for several years on its replacement, and has woken up in the last couple years and realized that while their infrastructure has been their competitive advantage to this point there is value in the whole industry having access to to their technology. Maybe I like their expertise and I'm not ready to condemn Kubernetes and its quality just yet because it's young and who knows where they'll go. Maybe they'll separate Omega from google3 and land it in Kubernetes. Then what?
Mesos and Mesosphere talk a lot about scale, with the implication that the technology you're modeling powers the entire Google fleet in one big harmonious system. It doesn't. There's a fairly hard upper limit on the system you mentioned in terms of scale, which is one of the motivations for Omega. The system you mentioned also fits into an ecosystem from a DLM[0] to a RPC system to a build system and on up. Pieces of that are gradually being open-sourced, too, like Bazel. Google is clearly becoming aware that their infrastructure being generally available will benefit the industry enormously, and regardless of my personal feelings on their business model and exploitation of user data, that is a good thing. If you're telling me that Mesos can do better than all of that expertise, better than John Wilkes, better than all of that, to the point where you don't even consider Kubernetes on the same path as Mesos, I don't know what to tell you other than come back to reality. This seems to be a rut with Apache projects that model Google systems in some way: Zookeeper, Mesos, Hadoop, Flume. All of them look like if I described the systems in question over a very blurry fax, and the open-source community did its best. That's not outright criticism, it's just having the unique experience of having seen their Google counterparts; it's a good thing they exist, but there are absolutely opportunities to do better, Mesos included.
I get what you're trying to do with Mesos, but I strongly disagree with your characterization of Mesosphere as a datacenter operating system. It's disingenuous, and positioning Mesosphere as the only company who can do hyperscale in containers is a tough sell. Last time I used Mesos, in 2012, it could barely handle 100 machines and I had to write shell scripts to even get a simple static application scheduled. I then threw 10,000 jobs at it and the scheduler hung and took down the entire cluster. Clearly you have come a long way since then, but it's apparently easy for you to forget that given the age of Kubernetes.
[0]: You'll pardon me if the thought of Zookeeper doesn't excite me as the backbone of the entire system.