How to install MacTeX 2015 successfully in El Capitan?
You are misreading the guide when defining the path for TeX programs in TeX Live Utility.


In TeX Live Utility, open Preferences
Click on "Choose"
Do one of the following


press Shift-Cmd-G, type /Libary/TeX, click on "Go", double-click on texbin and then click on "Choose"
press Shift-Cmd-G, type /Libary/TeX/texbin, click on "Go" and then click on "Choose"