The "tons of Ubuntu users and people who support diversity" are completely unimportant in both the Mir/Wayland and systemd cases. They don't contribute anything (except maybe a lot of drama), don't have the technical knowledge to decide anything and don't have to support anything. They're just spectators shouting from the tribunes.
systemd was resented by some users, but for developers it had so many advantages (especially stuff like logind) that a huge part of them just started happily using it.
As for Mir, I cannot think of a single discussion on any communications channel ever where a Non-Canonical developer thought it was a good idea. The GNOME people wouldn't even look at it. The KDE people openly stated that they hated it (http://www.mail-archive.com/ubuntu-devel@lists.ubuntu.com/ms... and https://blog.martin-graesslin.com/blog/2013/05/mir-in-kubunt...). No Non-Canonical developer ever added support for it to any UI toolkit. For me, that's very, very close to 'one voice'.