I think you are correct, however I also think many people at least try to roll their own, it's such great learning experience to try - touching the rendering th

I think you are correct, however I also think many people at least try to roll their own, it's such great learning experience to try - touching the rendering the physics all for yourself, even if it is only primitive. However I believe this will change in the future and we will go full circle back to people rolling their own for real world use... why? because modern real-time rendering engines are an amalgamation of hacks on how to get beleivability out of triangles and shaders, they are necessarily complex - to the extreme - and you cannot compete as an individual. However the future is clearly path-tracing or some form of ray based rendering (it's sustainable, the hardware has a future there - it's parallel), path tracing being a simpler unified model for rendering makes it's completely within the grasp of individual developers, this would open up a whole world of creativity.