I agree that one should have phased out coal faster instead of nuclear. Also with nuclear one needs dispatch-able power because demand is also variable and one does not use nuclear for balancing. But one certainly needs more with renewables. For the time being this is gas (which is a small fraction of overall gas use in Germany). In the long-term it will be replaced batteries for short duration and likely back-conversion of synthetic gas if there is a longer period. Biomass and demand-side electricity management will also help. Overall, I do not see a fundamental problem.
French PWRs routinely load-follow, ramping 1-5% of rated power per minute. With ~70% nuclear generation, they had no choice but to design for flexibility. Their N4 and newer reactors can operate between 20-100% power on demand.
This is not about technical possibility, but about economics. The cost of nuclear is capital cost while operating costs are small, you want to run your plant at maximum capacity.
