As someone who’s not an engineer I was able to design, draw& print most of the components for a M202 Rocket launcher and the only off the shelve parts I needed were a carbon fiber & aluminum tube. It’s fully functional and the rockets themselves are going to be a mix of printed parts and composite materials . I also had a Fliegerfaust printed mostly in 3d printed metal and worked great

The barrier to entry is constantly getting lower and the advancements in design are greatly increasing