Paladins were a 2 handed class way before WoW, with Arthas, Uther, and all other generic paladins you see are 2 handed users.
Now of course Protection paladins should use shields.
Holy should have the option to choose in BfA imo, with the dynamic stats on weapons these days.
The main reason 2 handers haven't been used in the past was stats on them, now any weapon they design could be int/agi/str if they wish.