An article in the Bulletin of the Atomic Scientists contends that thorium power isn't any more proliferation resistant than current uranium reactors: https://thebulletin.org/2018/08/thorium-power-has-a-protactinium-problem/. Having said that, the other claimed advantages appear to stand.

I believe the most attractive thorium technology, the molten salt reactor, also has corrosion issues which haven't yet been solved, though they might have been by now if it had been taken more seriously back in the day.