Comment by thot_experiment

False, if you're printing PLA or something sure, but you can print all sorts of exotic fiber reinforced materials, and maybe if you're clever enough you can even use the anisotropy of the print to give you extra strength in the relevant directions. I'm not claiming that it's possible to 3D print noctua quality fans, especially on consumer FDM machines, but I think "inability to find a rigid enough material" is not going to be the failure mode, at least not on it's own. I could believe "inability to find a rigid enough material that can also get the required surface quality".