Cold winter days don't represent peak consumption for the grid, there is no capacity being built specifically for cold winter days. In contrast there is capacity being built to offset everyone turning on the A/C during summer heatwaves, and solar has high power output during those periods.

Your argument is specifically called out as being a misuse of the "duck curve" concept.

> Common misconceptions

> One misconception related to the duck curve is that solar photovoltaic power does not help supply peak demand and therefore cannot replace other power plants. For example, in California, solar output is low at 7 pm when daily demand usually peaks.[19] This fact leads some to believe that solar power cannot reduce the need for other power plants, as they will still be needed at 7 pm when solar power output is low. However, California's annual demand peaks usually occur around 3 pm to 5 pm,[20] when solar power output is still substantial.[19] The reason that California's annual peak tends to be earlier than the daily peak is that California's annual peak usually occurs on hot days with large air conditioning loads, which tend to run more during midday.[21] As a result, solar power does in fact help supply peak demand and therefore can substitute for other sources of power.