You don't need these unreproducible parts for a rocket

Umm, could you help educate us. How do you know/state this so confidently?

The way I see it, there are roughly infinite previously non-constructible parts that by definition we as a society couldn't test. Now that we can construct these new parts, shouldn't we test them and then use them if they are better/cheaper?

Because, if such parts were really needed, people would've gone to any length to make them for things like missiles.

High performance heat exchangers for applications where every gram counts for example were hand made like a jewelry work at a huge expense.

I spent 10 years working in electronics, and not only manufacturing.

There have been rocket engines built by stacking carefully made thin metal slices (with holes cut for coolant channels) and then using diffusion bonding to join them into a single monolith. I could see 3D printing being used for this instead, and perhaps more cheaply.

I see even diffusion bonding still being cheaper than 3d.

I see, you just don’t believe that additive manufacturing is a truly new paradigm and that there are parts that can be constructed now that were previously just non-constructible.