I don't think Smite is overpowered.
I think it's about in the right place in 5E. It gets a disproportionate amount of attention simply because it's extremely impressive when it lands on a crit and just annihilates a monster, but I once tracked everyone's damage (and thus DPR because I also tracked fight round length) for several games, and he had a Pally, and he wasn't doing particularly high DPR, particularly not once overkill was taken into account.
So I'm definitely happy with Smite as is. It'll probably get totally unnecessarily nerfed in 1D&D though.