They didn't invest much into Upstart at all, and quickly announced a switch after Debian adopted systemd.
They still maintain Mir, as a Wayland display server.
Unity was one of the most popular desktop environments and brought Ubuntu users a lot of value over the years. It even influenced the design of GNOME 3.
I didn't understand much of the unity hate, especially compared to things like gnome 3. Really wish I could have HUD, combined titlebar/top panel, and typo-resilient search back. The latter two are possible with gnome extensions but don't work quite as well.
It's not so much hating what they do but the manner in which they do it. CLAs and not contributing upstream from the get-go means Canonical's special stuff cannot go further than Canonical.
Community forks of e.g. Unity have cropped up that ditch the CLA. Open source is open source, after all.
That said I do agree that the CLA has doomed most of their projects from gaining considerable adoption in the wider Linux community. At least while Canonical is still running the project.
Yeah I'm generally critical of Canonical for these moves, but Upstart is one I actually think was good and well done, as was their decision to move to systemd. Upstart was more pre-systemd anyway. IIRC Red Hat also used Upstart for a major release as well before moving all the way to systemd.
They still maintain Mir, as a Wayland display server.
Unity was one of the most popular desktop environments and brought Ubuntu users a lot of value over the years. It even influenced the design of GNOME 3.