If you look over the last 10 year, renewables have reduced the CO2 emissions considerably in Germany, reaching 50% in 2020. However, while 2020 was a record year with a huge increase vs. 2019, 2021 was back on the 2019 level, as the weather was very average.
It's a good thing, then, that that's a false dilemma and nuclear and/or fossil fuels are clearly not the only options on the table.
As a reference, Germany already relies on renewables to supply around 60% of their energy needs, and it's production is still ramping up.