Monju had many things wrong with the design, it was a loop-type reactor that nobody is talking about building anymore. Also it was nowhere near adequate from a seismic perspective it is kinda shocking they were allowed to build it at all.

Water reactors have no future for the same reason nobody has built a coal plant since 1980. The steam turbine and associated heat exchangers are unacceptably large and capital intensive compared to modern fossil fuel power plants based on gas turbines. (Look at how huge the steam generators are for the PWR)

Even if the construction problems were solved for the LWR, the economics will not work, you are better off capturing the carbon from a fossil fuel gas turbine plant and pumping it underground.

For nuclear power to be competitive we have to develop closed cycle gas turbine powersets. The 1970s model was that a fast reactor would be more capital intensive than an LWR but with the CCGT advanced reactors could be possibly be competitive -- if we can develop the powerset and reactors that run at high enough temperatures (not water) to support the powerset.