That is just misinformation. First of all, nuclear power never contributed that much anyway. If all nuclear power plants ever built in Germany were running at full load 24/7 for 365 days of the year, they would produce 231 TWh, which is less than 10% of our total energy demand. So there was never that big of a hole to fill in the first place. Especially in the last ten years, when only a handful of power plants were still in service.

In reality, renewables have managed to replace both nuclear power and a large chunk of fossil fuels (source). Last year we had to export enormous amounts of energy to France, because their nuclear plants had proven so unreliable (source). This has admittedly led to an increased use of fossil fuels, which we could have avoided by building more renewables here (or in France).