If we could overprovision solar and wind, we wouldn't have the problem now? I find that hard to believe. What happens when you need extra load at night or during a country wide lull in wind speed?

Nuclear reduces the need for peakers exactly because it can overprovision reliably.

You could also make nuclear peakers if you wanted reasonably easily too. Nuclear plants have tunable output to a point, they're just slow and hard to fully stop, so you would make a design optimized for very tunable output and high peak power. (0)

Solar and wind cannot suddenly overprovision. The sources either exist or not, you can at most ground them instead of collecting power.

0) IAEA - Non-baseload operation of nuclear power plants: https://www.iaea.org/publications/11104/non-baseload-operati...