You won't heat homes using electricity more efficiently than with direct heaters without significantly redesigning them, so all this would do would be using even more primary energy than before. This is going to happen over time as nZEBs according to the 2010 and 2012 EU directives are going to replace old buildings in the building stock, but you can't make that happen overnight.
Also, since the origin of the electricity doesn't matter in this case, to say that you'd need to not shut down those nuclear plants is clearly wrong since you could just use the currently underutilized coal plants to get exactly the same effect -- except the lack of electricity is clearly not a problem.
We're literally going into an era, where politicians are advising their citizens to "wear a warmer sweater" at home, in one of the strongest economies in the world. Every killowatt of energy helps, and if you're able to switch a percent or two of your people to use electricity for heat, that can save a lot of gas for areas, where there are no alternatives.
Yes, long term we can talk about many alternatives, but it's july... august, september, and it's already cold, space heaters cost ~10eur (2kW) and are still available (atleast more available than the alternatives).
It turned out that "strongest economies in the world" are like that by literally destroying the world's ecosystems. If you have any idea how "wear a warmer sweater" is a bad suggestion until we make it so that the destroying of the world's ecosystems is not necessary, out with it. Energy-efficiency-wise, wearing appropriate clothing is one of the best ideas.
Also, since the origin of the electricity doesn't matter in this case, to say that you'd need to not shut down those nuclear plants is clearly wrong since you could just use the currently underutilized coal plants to get exactly the same effect -- except the lack of electricity is clearly not a problem.