What socrates spoke is very interesting, in the point of helping us understand a bit of how it may have come to be like this ... History of playmobil.
In a way, I think System X is an improvement for modern city, school, firefighting, police, & cetera. (I don't mention space because, in my view, Playmobil was NEVER successful with it. Playmospace is cutey, but not _really_ interesting as space. (Imo.)
I agree with Gioginetto: what appears in diorama expos is Steck, up till now. (Steck & Victorian mansion.) However, a few interesting buildings with System X with the Magic Castles, for Arabian & Indian buildings, it can be used in an interesting way, and suits well ...
I like steck castles because of my childhood dreams. (The only thing I actually have is a blue framework house
... and of System X, the Magic Castle kitchen, which I bought because of furniture & bits mainly, but it has been useful as a room, once it's one of the few (that is 2) playmobil buildings I have. Despite being weird with the holes, & all, well, it is good to use. It may "not be playmobil" (I agree with that, in a way), but the klickys feel at home inside, once it is Playmobil-made.)
I simply wish they kept launching and selling steck as well. I'd love to see new medieval civilian sets. Steck framework houses are wonderful for it. I'd like to see new models of steck houses!
... have you ever imagined that? A Mill, a round framework tower ...
Steck has a lot of potential!
An interesting point that came to my mind yesterday was the fact that playmobil did an approach to extend steck to another world outside of the castles: They released the new generation of western houses in steck.
And they advanced them in a way that was novel: They added rigid ground floors.
(I purposely ignore here these strange black pesudo-floor pieces released before...)
So, I imagine they tried to extend steck. They also liked it. But these Western houses sucked. From my point of view especially due to the ground floors. They were static, not to be combined and completely contrary to a modular building system. At this point (well one year later) they introduced the SysX for city life and since then tried to establish this as being the major playmobil system. Obviously, they are also aware of the aesthetics of steck castles, as the introduction of the first sysX-castle took quite a while then...
Maybe it went this way...
best,
socrates