> there's nothing on the horizon
We can build more of what we have, such as pumped hydro and EU-wide interconnections.
You mentioned the fear that the solutions will cost 5 times more than nuclear. That's not a horrible worst case scenario (as nuclear is so cheap ;-) and we can be sure that costs go down as the markets scale and technologies mature.
It may look bleak in Germany at the moment, but it certainly doesn't look bleak everywhere or for long.
I don't believe they are solvable with the existing approaches. Transition to natural gas from coal is possible, but there's nothing on the horizon after that.
The existing plans (if you can call them that) mostly depend on asterisks pointing to a footnote saying "magic happens here": cheap hydrogen, power-to-gas, radically cheaper batteries, etc.
> For example, a simple thing where Germany could try to follow the Nordic countries is heat pump installations to keep houses warm without fossil fuels.
They are trying. But they are already having problems with very expensive electricity. Which will only get worse, as demand climbs with more heat pumps.