The problem is CAD is too broad a term here, and we are mostly sticking to "cad for designing physical stuff". Sketchup is certainly used by professionals, it

The problem is CAD is too broad a term here, and we are mostly sticking to "cad for designing physical stuff". Sketchup is certainly used by professionals, it has a number of niches where it's super successful. Particularly architecture and interior design, it's well used for quickly visualising and translating plans. You would never you it for product design, as you said. I think (maybe wrongly) most people in the thread will be thinking "3D Parametric Solid Modelling CAD for Product Design", such as SolidWorks or freeCad. Even if you build a "simple" app in that product category it will still have to tackle all the same hard problems in its kernel as a pro app. It maybe even needs to be more robust.