Hi,
this is tricky, I would agree with you, but then, it's necessarly the case in fact.
There are numerous UI solutions on the assets tore still, and many projects are not using the Unity UI.
PLus, the way Unity is evolving seems to indicate they are going for "Modular" approaches which I would suspect that soon you'll have to download specific modules, and the Unity main install would not have everything as it currently has. So I would think personnaly that for now we should be watching for how Unity will evolved and stay on the safe side of now including more custom actions that are specific to a particular module.
Bye,
Jean