I make a lot of papercraft props. Some for myself, sometimes for other people. Been dabbling in it for about four years now. My thoughts on it is it is not a bad way to get introduced into specifically armor building. It doesn't get much simpler than this especially if you're a beginner and have no idea how to draft patterns and to take those pieces of material and work it into armor and it's relatively cheap. If you screw up making your base piece with paper you've only lost maybe a couple bucks in paper and ink and then once that's done you can get some fiberglass and bam you have a piece you can use. So in that sense it's good. Me personally got my foot in the door into armor building and eventually learned the other great techniques that some of which are better options than papercraft.
But on the down side it's time consuming as all hell and takes a certain amount of patience I've learned not everybody has. Heck even I don't more than half the time which is why I still got stuff unfinished on my desk. Also mainly most people use fiberglass to strengthen their armor which is toxic and bad for your health and not everyone is able to get access to and to get a really good quality piece that requires lots of bondo and sanding. Hours upon hours and sanding and that can be hard to learn.
So overall I find using papercraft both an excellent tool but also a giant headache sometimes. I'm tired so I'll post some of my work later.