Build a terraced end house with an additional unit (GÜ) on your own

Well, it's a completely pointless discussion.
There are simply areas where the plots of land are so expensive that almost nobody can afford a detached house with 600+ m². Period. This is reflected in the parceling and the development plan.
Whether anyone from Pusemuckel finds it cramped or not is simply irrelevant.
The only alternative is to leave the area.
If you don't want to do that, you just buy the ridiculously expensive towel-sized plot and build your row house on it.
By the way, the result is often worth more / more expensive than the detached house out in the sticks.
There are also very good reasons why some areas are expensive and others are not.

I am not envying or bashing any owner of a detached single-family house here. But I very much enjoy bashing the nose-wrinkling about terraced houses on less than 700 m2 of land. They also have their purpose, and even if every citizen had the money to build freely on 700 m2 - there wouldn’t be enough space for it.

If you don't want that, just buy the ridiculously expensive towel plot and build your row house on it.

That's exactly how it looks - another alternative would then be the condominium, but compared to that the row house is another level altogether.

Because ... you then have stairs as a "goodie" inside the apartment?

Whether inside or outside does not matter at first. By the way, even a detached single-family house (ex bungalow) has stairs - according to rumors. The soundproofing is generally noticeably better and practically every terraced house has a garden - much less common with apartments. An owner-occupied apartment without an annoying owners' association is out of the question, with terraced houses it depends on the concept.

And we have a little DEER on 650m2 area^^. Why? Because in the past, this plot size was needed for growing pig feed and the animals' outdoor space, but the houses were small. Instead, we have a house in a prime location and are completely happy with it (four of us on 100m2, that’s enough for us).

I also find the discussion here very tedious. There is no alternative, they made their choice and as long as the biggest a**hole doesn’t move in as a neighbor, it will be a nice, quiet settlement where everyone knows everyone and the kids will be coming and going everywhere in a few years, making the street unsafe with balance bikes, bicycles, scooters, etc. That is all worth a lot. And if it gets too annoying, you simply sell the place again – because you will get rid of it immediately and without any loss.