But does this mean nuclear is uneconomical?

Nuclear energy costs about $170/MWh, coal about $100 and solar/wind about $50/MWh.

For comparison, the average price of electricity in the US in 2021 was $140/MWh.

It's almost guaranteed that in 2022 it will be much higher, because the jump in price of both natural gas and coal.

[1] https://www.eia.gov/todayinenergy/detail.php?id=51438

Solar/wind will always fluctuate - nuclear can provide a guaranteed output to smoothen the need for massive batteries.

Most nuclear power plants are designed for constant power output, so they still need some other thing (like batteries?).

Some are engineered for changing their output power quicker, but that means higher costs (lower usage), more complicated design and for short periods (<30 Minutes) some other energy source/sink while the power is adjusted.