Ever heard of a housing shortage? Probably affects sparsely populated, rural areas less, there are also refugees: "Up to 500,000 apartments needed for displaced Ukrainians" (Schlafzimmer 15.03) + the hundreds of thousands who are on the move due to the food crisis in Africa and the Middle East...
But the housing shortage is not caused by single-family homes that have been there and occupied since 19xx. And if we were to take in hundreds of thousands more people every year than we "lose" (emigrate, etc.), then our population would certainly increase more than the 0.2% reported for 2020.
It helps: the climate, the community (which has drifted apart due to Corona), efficiency (shopping or cooking for each other saves time and money, you would always have to rent 2 apartments to friendly couples/families). The GDR showed that cohesion can be lived/practiced in such an apartment building. That would do German, super individualistic and also selfish society good.
It does not help the climate if an already finished and functioning house is torn down to build a new one. Alone 8% of global CO² emissions come from cement production.
The climate would be pleased if existing buildings were upgraded and vacancies were fought.
Regarding cohesion, I agree with you that there is a lot to be gained here. But I don’t have to evict old people from their houses for that.
Especially in the areas where people aged 85+ have lived in their houses for decades, there is usually exactly this cohesion. Just like here with us, it has nothing to do with apartment buildings vs. single-family houses, but only with the mentality of the residents.