To make sure that no other packages like eg base-files suddenly start adding these kind of packages you might want to add to /etc/apt/preferences or prolly better a file like /etc/apt/preferences.d/dontwant something like:
Package: avahi-daemon canonical-census
Pin: release v=dontwant,a=dontwant
Pin-Priority: 1001
This will block two annoying packages that don't belong on most servers.
avahi, because you don't need to announce everywhere when your server is located somewhere in a DC (indeed it might be handy in a local network, but it stops being useful when you don't have multicast routing and/or have a routed network)
canonical-census, because Ubuntu does not need to know what your server is doing.
Of course other packages can be blocked in a similar way from being auto-added by apt. (unfortunately a dpkg 'hold' does not work).
Another way is to make a fake empty package, then the depends are satisfied, in the above case you might have packages which refuse to install because the package can't be found. Do make sure with 'apt-cache policy' to see if you don't have other apt-prefs at a prio of 1001 (or higher if that is possible) otherwise they might still get there.
I am also wondering when Ubuntu/Redhat and other such commercial "Linux" companies start being nice to all the people who actually do the hard work and start acknowledging that those people are what they are selling/supporting/consulting on and earning money with.