Nuclear is also "gas-backed" in way. A stable energy grid is not something one can hand wave together.
Nuclear is reliable to a fault. It is rock solid. But it doesn't "go up" very fast - that is where you need gas support. Which is quite different from solar and wind, where you can't predict the ups and downs
Have you looked at France's grid recently?
In Germany it was backed by water power that could take most of the load at night so that the nuclear power plants could run continuously.