Nuclear currently has a huge range of issues that’s outside of reactor design. Even assuming a 50% cost reduction seems viable, it’s still expensive.
Permit’s and regulation are real and significant costs. In an ideal world they would be lower, but realistically you need to consider them
Next, load following is critical as renewable energy regulatory reduces the spot price of electricity near zero. Breakeven right now is an average around 12c/kWh 24/7 if you’re capacity factor is cut in half then you need to be selling near 24c/kWh for that half. This is more or less still true even if you get to run 24/7 as the value of energy produced still drops. A ~50% price drop clearly helps, but the core issue remains.
As to the design, it’s inherently more complex than a gas turbine due to the need for shielding etc. Next, the fuel assembly is surprisingly expensive $1390 per kg up front which provides about 40kw for a year or 0.4c/kWh. And then you need to deal with 1kg of high level Nuclear Waste. Eventually you need to decommission things and that’s even more inherent costs.
Sure, some costs can come down like the current 500 to 1,000 workers per GW of capacity. But, Nuclear is already reviving subsidies in the west so it needs to be vastly less expensive to become viable.
PS: Yes compared to coal fuel is cheap, but compared to 2c/kWh solar that’s eating up significant budget for something considered cheap in the Nuclear world.