If you could leave nuclear, and "replace" lignite with wind and solar instead, you actually replaced nuclear with lignite.

>The decision to phase out nuclear has long been made (for good reasons).

No, it was made for bad reasons.

>Keeping them active or even building new reactors of that kind is not an economically viable solution. The price Germany pays for this is higher carbon emissions for the time being until renewables push coal out of the mix. What Germany gains, on the other hand, is the removal of the most expensive form of energy

_Existing_ nuclear reactors are the cheapest possible source of electricity. You already had to build them and will have to close them. Left is the cheapest part, of actually operating them.