That's a typical objection of people who haven't studied the details.

The engineers who are behind such proposals and plans actually now that sun and wind energy isn't constantly available. That's way there is a mix of energy sources and technologies, including, yes, Russian gas. But also American Liquified Natural Gas. Oil. Electricity storage systems. And maybe even new nuclear reactors in the future, once a few nagging problems have been figured out.

There are great engineers for sure in Germany. Not everybody left for Valley or Switzerland. But having 2nd most expensive electricity in Europe is a crystal clear result of bad engineering.