better insulation is not cheap and therefore not everyone can afford to do it. Also the same people who want renewables are usually opposed to building new housing so there's that.
This makes insulating this house an absurdly bad financial decision, since once you have moisture damage in any part of this material, you can basically demolish most of the walls since it soaks like a sponge.
Mind you, I have not started going into the pitfalls of the legality of even touching a house this old in Germany, where you have to deal with "Denkmalschutz".
Insulating new construction and retrofitting insulation are two absolutely different things and barely have anything to do with each other from the cost-benefit ratio.
My house in Sweden is from the 1950's and I still had to be _very_ mindful when adding insulation. The best thing I've found is cellulose-based insulation, basically shredded newspapers lined with salts and pressed to sheets. The can buffer a lot of moisture without developing mold.
As the article notes this price decline was predictable decades ago, but you can't really blame people for being dubious about predictions. Maybe the people who got it right were just lucky.
But since real actual installed wind and solar became cheaper a while ago, the people still openly arguing against renewables slide ever close to cartoon supervillain status.
What? Why would you think that?
Plus, people usually oppose nuclear which is an expensive but stable renewable option.
