Ghost guns cannot be made entirely from consumer grade 3d printable parts, they require machined components such as firing pins and barrels so that the gun would fire reliably.
If this was about safety, why not police the purchase of said components?
Because it's not about safety. It's about making sure that you have less control. And especially so you can't create or repair the things you own. Because that would be harmful to the capitalists in charge.
Why do you think cars have gotten more and more complex over time and you're not allowed to repair them?

