It isn't.
ALL factory and most aftermarket stocks come with horridly loose inletting. This is called a 'drop in fit'. Problem, they don't state which action will drop in
So proper bedding is a necessity for peak performance. Some of the worst inletting I have seen came from a very big name stock that cost quite a few pennies to buy.
What most aftermarket stocks provide is a more rigid structure. Whether laminated wood, composite or alum chassis/plastic overlay, these stocks are rigid in torsion and flex.
I am playing with the Choate tactical and it feels like you could use one to jack up a truck - solid.
BUT the inletting is generous and I will properly bed it for best function.
The plastic factory stocks can have some very nice features. The pillars in them tend to be massive which is a good thing and the plastics used can have bedding compound stick to it with some prep work.
So the only weak area is the forend. Here you can either open it up ALOT and/or reinforce it to be more rigid.
I have been hunting and LR shooting with these plastic stocks for a long time with no problem. Are they ideal? NO. But they can be made to work.
Just playing with Savages new Edge/Axis. The erogonomics and appearance on this stock is excellent AND it isn't all that bad for flex. The inletting is also unique and may be one of the best I have seen in a factory rifle. Yes, a $300 rifle having "best" as part of its description.
Proper engineering and design is the limiting factor. The material is actually quite good.
Jerry