You wrong as hell lmao. Gone are the days of Cody Wilson's proof-of-concept The Liberator, people are printing chairmanwon glock lowers, FGC2.0s, 3011s, Hoffman AR lowers, etc, they've even got full ass CETME lowers now.
They have metal parts you can get without a background check, yes, but you can print the regulated part and they last a good couple thousand rounds. Not as sturdy as injection molded polymer but good enough to get "the job" done unless you're like, deployed to Fallujah.
And also: they'll never be able to stop it. This won't work.