bzr: no longer in active development.
Landscape: very well established.
Mir: not really a wide-reaching project (AFAICT). It fits in between existing well-defined APIs (a handful of toolkits on one side, and hardware on the other), and can be implemented fairly independently by a separate team.
That doesn't leave very much to "spread themselves so thin". It comes down to spreading over two main areas: client devices, and cloud.
With client devices, it makes sense to cover multiple form factors with a single code base. That's Unity 8 across phones, tablets, etc. That's not spreading out to me; it's just being smart about code re-use.
With cloud, it makes sense to look at Openstack on the host and transactional updates on the guest. That's hardly "thin".
Dropping bzr from active development is surely an illustration of how "spreading themselves so thin" exactly what Canonical is not doing?
Naming a pile of buzzwords doesn't by itself provide any evidence of your claim. Especially when some of these are flat out wrong because they (quite publicly) aren't under active development any more.
> seeing what sticks
Upstart remains excellent and nothing else existed at the time. It preceded systemd by a large margin. bzr is much the same. It pre-dates git.
In [1], Jelmer Vernooij writes: "Some people claimed Bazaar did not have many community contributions, and was entirely developed inside of Canonical's walled garden. The irony of that was that while it is true that a large part of Bazaar was written by Canonical employees, that was mostly because Canonical had been hiring people who were contributing to Bazaar - most of which would then ended up working on other code inside of Canonical."
It isn't so much that Canonical conceives of a project and goes off on its own direction; more that Canonical ends up hiring community members who are already contributing, who then make decisions they would have made anyway but with Canonical hats on, and larger community less aware of the details attribute this to some kind of secret internal Canonical policy decision.
I think that neither of these were about "seeing what sticks", since at the time they were conceived there weren't any other clear alternatives. And nothing else in your list is yet unstuck, so that hardly demonstrates that this is some kind of policy here.
Disclosure: I work for Canonical (but here I speak for myself, not for Canonical).
[1]: https://www.stationary-traveller.eu/pages/bzr-a-retrospectiv...