FDM 3D printing is as in this case is not in any way structurally sound. I use it frequently as the least expensive way to make test fit prototypes before investing in either injection molds or CNC machining. The best means of “3D printing” not local to my office is a laser sintered (SLS) fiberglass filled nylon and/or metal powders. The nylon parts are strong enough to be used in low volume production runs.
I use a company that also makes complete car body parts and even engine parts like intakes and valve covers for the prototype future models of cars to be tested for fit and even initial aerodynamics testing.
I have never found the FDM processes to be nothing more than making look-alike that cannot be used for anything other than fit.