Construction costs are currently skyrocketing

Which ones? IG Metall, as probably the biggest collective agreement, expires this year….

Nominally I agree with you - but: if the rest of the salary in terms of purchasing power becomes so little that it’s no longer enough to maintain the property because people have other needs, then what? Somehow the house also has to be heated, someone has to commute to work, and something warm has to be put on the table. The consumer loan has to be repaid every month, the hair has to be cut, and the water bill has to be paid too. What then? Just take a look at many financial plans here, many people are quite naked about all this in the finance threads, and it’s often pretty tricky especially in the first years after building a house.

I already gave my example. With a 10% nominal interest rate, it makes sense to repay as quickly as possible. However, if I pay 1.63% with a 30-year fixed interest period, it doesn't make sense to put liquid funds or surpluses into rapid repayment. Especially when inflation is higher than 1.63%. Possible special repayments or a higher repayment rate I prefer to put into products with higher returns (stocks, ETFs) and pay 1.63% faithfully for 30 years or let inflation (assuming my salary increases more than 1.63% and roughly in line with inflation over time) pay off my loan and I enjoy the money or the profits I generate with it and can spend.

"Wealth building" and "retirement provision" do not imply return optimization or exclude a "safe" financing with initially worse conditions and fixed interest over the entire term from building wealth or provision.

Sure, if I have a job where I cannot expect any wage increases, it will get tight at some point. But honestly: if I were already working in such a field (no collective agreement, no opportunities for advancement), I wouldn’t even get into debt because of a property. Although someone in such a situation shouldn’t really be renting either.

Basically, you're right, but there are two problems. The first problem you mentioned in your last sentence. The vast majority consume the supposed savings and do not invest it. If there is an emergency, there is no money, and the 10% house you own has to be sold, no matter what the prices are because the potential buyer now has to finance at 5%.
The second problem is that interest rates and the stock market are not as independent as you make them out to be. Inflation in tangible assets like stocks and real estate has been a topic for some time now. And if you look back at what happened in the past, you see that the 70s were a terrible time for stocks. Entering with high valuations, exiting with low valuations, and in between, steadily losing to inflation.

Anyone can invest their money poorly if they want. But then it shouldn't be called wealth building anymore. And if I make the bank the landlord because at 4% interest I only get about 1-1.5% initial repayment, then you simply don't build wealth anymore. Quite simply