Nomad, on the other hand, is pretty simple and easy to run, and a single binary. There's probably no benefit to having a managed offering.
That said, I wouldn't be surprised if HashiCorp add Nomad to HashiCorp Cloud Platform, which currently lets you deploy Consul and Vault to cloud providers via their system.
Which is to say it's useful enough to a large amount of people to make it viable as a product offering. Nomad would fail as a managed offering here like like Deis, Flynn, Convox and probably 100 other container management platforms that came before.
As a niche tool to manage sub-1000 boxen it's probably ok. But k8s has won the greater war.
Disclaimer: Worked on Flynn, still run it for my own personal stuff by $DAY_JOB is all k8s.
Your enumeration of the managed things is very particular, in that it includes only stores. There's a reason for things that have keeping persistent state as their reason to exist are managed: reliably maintaining persistent state in the cloud is a lot more difficult than reliably orchestrating things that just have to run.
Managed _something_ does not mean it's "mind-bendingly complex", but rather that people don't want to take care about it and focus on their own stuff like building applications.