The functional core components of a Glock are not made from organic polymers, for a reason.

Neither are the core functional parts on a 3D printed glock. They use the exact same pressure bearing components, because those components are easily available. What's less available is a frame, and 3D printing solves that problem.

It is really like with all those other tools that can produce such a frame just as well.

What other tools? What other tools are available that can produce a glock frame of similar quality and with similar ease as a decent quality 3D printer for a similar price? (~$300)

But then, if you say most people print it with PLA you might have a strong point that most people 3d printing that don’t know what they are doing or don’t care about PLA’s serious limitations for that application, and do it anyway.

They know perfectly well what they doing and that PLA is a perfectly viable material for the application. Glock frames are not pressure bearing parts, and PLA is plenty strong. I'm saying this with confidence because it is not a hypothetical. People have built these guns and shot thousands of rounds through them without issue.

I wouldn’t consider using a 3D printed jig … and ECM as a part being produced by 3d printing. A helper part is for producing it by other means is 3d printed. Again, plenty of alternative methods to do so.

You don't have to consider it, it's been done and it works. Making rifled barrels is not trivial. This method is certainly possible without 3D printing but is made much easier with 3D printing. What is another method of producing a rifled 9x19 barrel at home that's easier than 3D printing a jig, and running some chemicals through hydraulic tubing with a fishtank pump in a bucket? Please link an example.

Are they all going to be restricted?

I don't know. I'm not advocating for restrictions. People have been making guns at home in the United States since before the founding of the country and they will continue to do so whether it's legal or not, regardless of the availability of 3D printers. Even trying to regulate the printers themselves is assinine, there's too many open source designs and software. Anyone sufficient motivated will get one. Trying to regulate printers in the name of gun violence is a none solution to problem that barely exists.

All I'm saying is that 3D printing has absolutely made the home manufacturing of firearms more accessible than it has ever been, and those firearms are perfectly viable weapons.