I've seen it argued that any "indirect" energy source, such as coal burning to boil water,
nuclear to boil water,
and then steam --> electrical,
is going to lose out on cost to any "direct" energy source,
such as solar-->electrical,
natural gas turbine-->electrical.
The argument is that the extra capital involved in the intermediate steam conversion step is going to price "indirect" power generation above all direct means.
This seems to be borne out somewhat in the real world, in that in the USA all new electrical generation capacity is overwhelmingly in "direct" conversion. This is largely driven by inexpensive natural gas, but there's plenty of solar and wind capacity being installed, too.
By this argument, both nuclear fusion and nuclear fission aren't going to be economical, ever.
Check out this report from the US DOE:
It forecasts the cost of nuclear, either fission or fusion, to be higher than pretty much all alternatives. I'm not sure whether this includes externalities such as environmental damage from CO2 emissions, but that would seem to favor wind/solar even more, and these were already the winners based on cost.
Maybe nuclear power might still make economic sense for baseload applications, but if energy storage options become cheap enough (battery technology is being worked on feverishly worldwide), then nuclear plants will be relegated to niches where solar/wind/gas can't work....
The "killer app" for fission/fusion might be for energy in space, not on earth. Can't use solar very well out past the orbit of Mars, and if you're mining asteroids, there isn't going to be any wind either.