Home financing ever possible? Probably not!

I can only say: build up reserves.

Exactly, everyone is warned now. For efficiency D, 90% of the buildings should also have new windows, basement and ceiling insulation. Only then can you start considering the heat pump.
There are still 10 years. Then there will be 3 age groups.
The 80-year-old grandma will statistically no longer have to worry about it.
Pensioners aged between 60 and 75. That is the critical group. Depending on the pension, not much can be saved anymore. This requires a solution, e.g. 30% of the property value goes to the state after death, in exchange for an interest-free loan.
Everyone under 60 still has enough time and is still working for a long time. The investment in windows + ceiling insulation(s) in EL can be realized with 30k. That is not unrealistic if you have properly calculated the maintenance reserves.
Landlords must also be addressed. "The tenant pays" can and must not be an option.

Some solution of this kind will have to be found, yes. The state provides interest-free loans or even advances part of the financing. This will then be passed on to the heirs later or something similar. But it can only be a loan... we cannot give owners of older buildings the long overdue renovation as a gift.

If you nowadays just had the feeling that such ideas generally made sense. I have had an electric car for 3 years. Yesterday I charged publicly for 59 cents per kWh. That means driving 100 km now costs me quite a bit more than it did with my gasoline car. A few years ago, however, we were still told how great everything would be for us with electric cars. But we are scrapping cars that could have lasted a long time. It seems to me that the same is happening now with the heating systems. We are destroying everything that could have run for a long time. Meanwhile, my neighbor is heating his 300 sqm house with wood chips, and on paper, that's environmentally friendly. Every day, I watch the smoke billowing from his chimney and slowly think to myself, they all want to fool me!

Nevertheless, your writing clearly shows that landlords must also be held accountable. I don't think it's right that all heating costs fall solely on the tenant. 350kWh/m2? No matter, the tenant pays.

Although some quotas on the CO2 tax are the wrong approach. The tenant only pays because many housing markets are dominated by scarcity. Just imagine if the tenant had a real choice between good and bad apartments. Then they would vote with their feet. So now the landlord simply adds the €20 contribution to the CO2 tax on top again. Because most apartment buildings are not that bad. The old building apparently had efficiency class B, despite unrenovated housing construction from the 80s, with exterior walls made of 20cm reinforced concrete. With 7 apartments per floor and 9 floors, there are hardly any exterior walls on average, and the energy certificate is calculated once for the whole building and not per apartment. I wonder then, what kind of building fabric an apartment building in class F or G must have.

If nowadays you just had the feeling that such ideas would make sense overall. I have had an electric car for 3 years. Yesterday I refueled publicly for 59 cents per kWh. That makes 100 km now cost me quite a bit more than it costs me with my petrol car. A few years ago, however, we were still told how great it would all be for us with electric cars. But we scrap cars that would have lasted a long time. That’s how it seems to me now with the heating systems. We are destroying everything that could have lasted a long time. At the same time, my neighbor heats his 300 sqm house with wood chips and on paper that is environmentally friendly. Every day I look at the smoke clouds from his chimney and slowly start to think they all want to fool me!

How many kWh does your e-car need for 100 km? Even at 59 cents (which of course is not a great price, no question) you’re only at about €11 for, say, 19 kWh per 100 km? If you want to go 100 km with a petrol car for €11, it must not consume more than 6.3 liters. That is at most achieved by a small car.

When it comes to burning wood chips and the smoke clouds, of course, one has to criticize if we do this on such a scale that healthy forests are cut down for it. That certainly becomes critical. Nevertheless, from a CO2 balance perspective, it makes a big difference whether we burn things that are already part of the natural CO2 cycle, like wood, or things like natural gas/oil, where we essentially dig up dead dinosaurs from the earth and introduce additional CO2 that our cycle cannot absorb.

a solution, e.g. 30% of the building value goes to the state after death, in return interest-free loan.

I don't think the state has to do that. There are providers who buy houses and you can continue living there. Whether that makes economic sense is another matter.
If a house is the only retirement provision, then you probably have to separate yourself from the house one way or another.