Tools & Fabrication - custom intake manifold

I have made a lot of intake manifolds based on what i was told back in the late 70s but now i am told that the old way of doing thing are not the same any more .
Have i lost my way with today's new intake manifolds??

what is the right shape and size for today's engine???
i have looked around and i see intake's like what i am doing so what am i missing