The problem at the root cause is the public's (reasonable!) expectations about safety. Humanity has experienced twice just how much damage a nuclear reactor blowing up can cause, not to mention how brittle they are and how lax people treat safety - just look at how many accidents happened at Sellafield - or the terrorism risk. Many of the experimental design ideas add the question of nuclear weapons proliferation on top.

Accounting for all these risks takes up serious amounts of money, enough to make the construction of a new plant so expensive it literally cannot ever turn a profit against incredibly cheap solar energy and ever-cheaper battery or molten-salt storage.

One might even say that nuclear energy was never profitable because the only way it appeared to be cheap was that the general public took up an extremely risky bet that the reactors would not go boom and because the costs for teardown and storage were never really accounted for.