There are actually many different communities and businesses online built around creating, sharing, or selling 3D shapes. Here are a few:
Plus there are many other sites you can find by Googling terms like "3d downloads" or "3d assets". Or if you know what you're looking for, search for it directly. For instance, "3d robot arm download".
We've had some internal discussions regarding repositories of 3D shapes. FlexSim may or may not become more involved in collecting and curating 3D shapes in the future, but for now we are not in the 3D shape business. Currently our focus is on the simulation software, and we leave the 3D shapes to those businesses/communities dedicated around that.