Because now your inflexible base-load has increased. And while spreading generation over a wider area helps, it rapidly reaches limits (unless your power grid extends close to the equator).
In a country where heating isn't yet electrified, it's a way to reduce fossil fuel use and carbon emissions (the ultimate goal) without necessarily reducing the fossil electricity production. So even if it doesn't solve Dunkelflaute alone, it's a part of solving the climate and energy crises.
This is not _too_ bad in itself, using gas for generation and then powering heat pumps is more efficient than burning gas for heating. But the capital requirements for new power plants will cement Germany's dependence on fossil fuels for at least another 2 decades.
It's a mess.
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.
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.