I hope you realize that there IS wingflex, no matter how much you deny it. it is unfair to compare trying to move the wing by hand, to what the wing does when the airplane is airbore with high wing loading, in a scenario where the pilot pulls up (rotation, upset recovery etc) or turbulence.
Implementing wingflex in PlaneMaker is simple and takes mere minutes. A small value that makes the wingtips flex a bit in moderate turbulence or high positive G is enough, and would add a lot.
Here a CL650 video showing some wingflex during normal approach in light chop. It's not much, but clearly visible. Yes it's a stiff wing. BUt it does flex.