The plastic bits should be taken off for real off road use. Then the car should be properly cleaned afterward.

Hell, even my 2008 Jeep Rubicon came with a plastic front/rear bumper and plastic air dam. It is one of the most capable off road vehicles ever made and still requires minor modification from factory form to be used properly.

There are things that the factory *must* do to sell a car. Like fuel savings plastic under parts. I would hardly blame this on the factory. YOU left all the mud in there.