You make a good point - starting from scratch requires too much effort to see any reward, but I think a simple, relatively stripped-down system is easier to understand and easier to build upon. A batteries-included setup can be an impediment to learning. When something is working, there is less motivation to learn how it works. After all, how many Windows users ever take a look behind the curtain?

From my perspective, a stripped-down system is like a set of wood blocks, and a batteries-included system is like a doll house.

If you give a child a doll house, the child could reverse-engineer the doll house to figure out how it was built, and to customise it, but the child will probably just play with it as-is, and focus on setting up doll furniture and re-enacting domestic life.

If you give the child wood blocks, the child will have to build a house for the dolls. The child will have to figure out how to make it structurally sound, how to make a gabled roof, how to make holes in a wall for windows, how to make a porch, etc. Of course, if they have never seen a doll house, it may never occur to them to build one, but they will probably build something. Later the child may progress to customising blocks, or making new blocks, or even full carpentry, building upon the earlier skill-set.

But, like you say, if you just give the child a felled tree, it is unlikely that they will figure out how to turn it into blocks, or into a doll house, or anything really. It's too big of a leap for them to make.