GGG, It's Time To Move On To The 21st Century, Or, Why DirectX 9 is a Bad Idea

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But you're not a software engineer so you don't know the impact DX12 has on draw-call limited performance bottlenecks when properly coded for it.

On the contrary I'm software engineer. :-) The draw call methods have been there before DirectX 9.
And in this regards I doubt there are any significant changes in the DirectX framework.
The new versions of DirectX are for some time mainly about new features unlocked for new graphic cards.

Sometimes that can help to squeeze more performance or do some nice additional effects, but the basics are well there in DirectX 9 present. However, most likely tesselation shaders would be useful from DirectX 11 version to speed up so called particle billboard systems.



Edited: corrected tesselation shader mistake (present from DX11)