Buy now or wait a little longer?

And when it comes to luck with the craftsmen... then no one should be building solid structures anymore, because all solid construction contractors have subs. No one has all trades in-house.

This is not a peculiarity of the Steiners, the Holzers also do not have all trades employed. Those who do are usually more general builders than general contractors, and above all: typically too large to serve amateur builders with single-family homes. A self-builder is better served by a general contractor of manageable size, and subcontractors are not a general fault (and incidentally required by the master craftsman obligation in many trades). Economically unhealthy/risky company sizes offer no advantage to the customer.

Town & Country simply stands for junk here...

I'll put it this way: with handpicked franchisees, it takes considerably longer to gain market share. I find Town & Country considerably more likeable than Heinz von Heiden. The big Holzers have completely different structures (and many of them operate on the principle "Private equity buys a name that had the image fitting the target market segment during the heyday of the timber frame panel builders").

Exactly this is also my approach. I grew up with two siblings in a well-planned 125 sqm house. Our rooms were each 12.x sqm in size. It was completely sufficient. There was a small office, the parents' bedroom, and a spacious living room with an open kitchen. The bathrooms and laundry room were small but completely sufficient. If we were to build a house, we would use this floor plan as a guide. We parents have always taken the smallest room/worst layout so far and are doing very well with it. I would also move into the attic or somewhere else. It just has to be in the house ;)
More space is of course always welcome, but I don’t want to be financially “enslaved” by the house just because I built beyond my financial reality.
But probably everyone has different demands/needs.

Back to topic:

With a house of 120-125 sqm, you probably won’t have more space than in your apartment. And with the land prices in your search area (at best) on an unfavorable plot. And for that, you are tying up your financial leeway for many years.

Stay in your apartment or move further out. Where you want to have a house, it’s not doable within that budget. The location is too urban (or close to the city) and therefore too expensive for you. That is the reality. Land prices have passed their low point. They won’t get any cheaper.

With a house of 120-125 sqm, you probably won't have more space than in your apartment. And that at the land prices in your search area (at best) on an unfavorable plot. And for that, you commit your financial flexibility for many years.

That is actually the central question for a home: "Is it an upgrade to the current situation?" – for example in the form of a more favorable layout for the same money, fear of rent increases eliminated without having to downsize, or something similar; the "same or better" is individual for every family and every situation.
If you can completely ignore the standard "do our dumbest acquaintances envy us?", you are already closer to the light than most other daydreamers.

If you can completely ignore the scale "do our dumbest acquaintances envy us?"

the base prices of 700€/sqm, and Berlin plots of 900-1200sqm, should lead to shared plots with your nicest acquaintances. Maybe change the search mask once

That is actually the central question about owning a home: "is it an upgrade from the current situation?" – for example in the form of better layout for the same money, fear of rent increases eliminated without having to downsize, or something similar; the "same or better" is individual for every family and every situation.
If you can completely disregard the standard "do our dumbest acquaintances envy us?", you are already closer to the light than most dreamers who keep going.

For us, it was simply the desire for direct garden access from the living floor that made us build a new house

We live as 5 people in 128 sqm (ground floor, 1st floor (partly with sloped ceilings from about 1.80m or something like that), attic, and basement) I like our house a lot, but if we had built new, then definitely with a bit more square meters, because it is quite cozy like this or the space is not always on the right floor for the corresponding things. So whether this would be an upgrade for you compared to your current situation, you have to assess.