Construction costs are currently skyrocketing

I haven't been able to follow this thread as closely recently, but I wanted to add the following: Since it has occasionally been speculated here that property prices in the (also older) existing stock will significantly decline in the medium to long term due to pressure from politics regarding various energy-related requirements/restrictions (gas heating, poor insulation...), I recently had the opportunity to speak professionally with architects, engineers, and auditors in the field of sustainable construction. They said that the opposite will be the case. Since the pressure mainly arises from the fact that existing buildings are the biggest CO2 emitters due to densification and energy-efficient renovation, the future (environmental) political focus will be entirely on this – or it already is. This will, of course, be reflected primarily in corresponding incentives through subsidies. I’m not writing this because we ourselves live in existing buildings ;)

Have fun installing the child seat first in an unfamiliar car, then uninstalling it again at the destination, carrying it through the city for 2 hours, and doing the same on the way back. That's somewhat impractical.
There are trips where the concept makes sense. And there are many trips where the concept doesn't make much sense. In the end, it usually affects those for whom it doesn't make sense.

Those who don't want that will have to spend 30% of their income on their own vehicle. If you can and want to do that. Great. The vast majority will no longer be able to do that... I already wonder today how people with an income of less than 1,500 net can even afford a car...

Those who do not want that will then have to spend 30% of their income on their own vehicle. If you can and want to do that. Great. The absolute majority will no longer be able to.. I already wonder today how people with an income <1,500 net can even afford a car...

If politics are conducted with your attitude, it is no wonder that the political extremes are growing stronger with the reference to "the good old days." As a society, you can decide to push through solutions that work well to reasonably well for a larger part and not at all for the rest. Or you choose to include the entire society as much as possible and find a solution that works for everyone. In the long run, you will fare better with the second solution, even if it offers fewer "simple solutions."

I have also dealt with this topic since we have 2 children. They are now 7 and 9. However, there is always a booster seat in the carsharing cars. That is not a satisfactory solution for me either, because proper child seats are safer. And with smaller children, it's out of the question; they need a baby seat or a rear-facing seat. In this respect, I completely agree with you. Then you could only use carsharing if you don’t return the car in between, but continue renting it. And then it becomes financially interesting because the clock keeps running.

Ever booked a hotel? How do you do it? Just click on any room and hope there’s a double bed and an extra bed inside? I always specify the number of people, the age of the children, whether I want breakfast, etc., and then the hotel finds the right room for me...

There will be carsharing cars without child seats and some with child seats. There will be small cars if only one person wants to drive and there will be large cars if you want to go to Ikea or the hardware store...

And maybe there are also people who retrofitting the cars as needed. Just like at Sixt. If I book 2 child seats there, an employee installs them... they don’t have 20 cars with child seats permanently parked in the lot.

If politics is conducted with your attitude, one should not be surprised that the political extremes are becoming stronger with reference to "the good old days."

The "good old days" are over because they were based on the fact that a large part of the world would never come to prosperity and did not even aim for it. That is definitely over; Chinese, Indians, Brazilians... they all want to live like us in the future.

If you want to go back to the Brandt years, then I can safely tell you:
Forget it. We will lose prosperity, not gain it.

PS:
The correct wording would be "Back to the bosom of Willy Brandt" ;)

Ever booked a hotel before? How do you do it? Just click on any room and hope there’s a double bed and an extra bed inside? I always enter the number of people, the age of the kids, and then the hotel finds the suitable room for me...

There will be carsharing cars without child seats and ones with child seats. There will be small cars if only one person wants to drive, and there will be big cars if you want to go to Ikea or to the hardware store...

And maybe there are also people who convert the cars accordingly when needed. Like at Sixt. When I book 2 child seats there, an employee installs them... they don’t have 20 cars with child seats permanently in the lot.

Nope, our carsharing provider has a child seat in EVERY car. Of course, you have to check how it is for your own provider. But the solution was chosen exactly so that parents don’t have to plan extensively. Those who want more could register, but then it obviously can’t be so spontaneous. It’s just not as super comfortable as owning your own car, well, whatever. It’s enough for us; for the second child, we would either have to register or bring our own booster seat. I consider that absolutely doable. It just doesn’t work without a bit of loss of convenience.