Fusion is also based on basic physical principles. Do you think a plant to cut all funding for renewables or fission and putting it into fusion research amounts to a sound energy policy? Sound approaches to decarbonization are based on technologies that are currently available, not ones that might become available depending on the outcomes of research and development.

Nuclear plants definitely could use thermal storage, but the main advantage is of nuclear over renewables is that they have consistent energy production and thus don't need storage in the first place. It doesn't suffer from the duck curve like solar, or weather-dependent intermittency like wind. Nuclear doesn't need storage to become viable, as France has demonstrated for decades.