Its a nice idea and i do feel that players should know more about how to make shapes, but seriously.. Everyone or mostly everyone has learned what shapes are, what they look like, and not to mention kids, teens, and adults have had access to building blocks and lego's for an extremely long time... I think if a player were to use their heads and a little bit of imagination. Then there would be a lot more builders.
..Come to think of it, you only have to look at a cars wheel in real life to get a good idea how to construct a circle on minecraft.
Or better yet. Take a piece of paper, a pencil, draw a circle, then draw straight lines or little boxes on that circle to understand how to construct circles in minecraft.
Sadly though, that does not seem to be the case in nearly 90% of the population that comes here.
To be blunt. If a player is unable to figure out how to figure out how to make a simple circle, triangle, or any other shape other than a square. Then they don't deserve even a recruit rank, little alone builder.
I know a sound harsh, but it's just a fact.