The first cars were silly when they were first invented. You could out walk or outrun them, but with innovation, they got better. It’s no different with these guns. They may have very limited usefulness where they currently stand, but with innovation, they’ll get better.
It’s only silly because I can make one that’s better from old plumbing leftovers, and it will never blow up.
Free zip guns have been around for as long as there have been guns.
It’s neat as far as 3D printing goes, and I’d love to play with that sort of stuff.
But the gun is just a novelty, and will remain so for quite a while, imo.
Not to mention that an actual reliable working modern gun is very cheap. $150 new and maybe $50 used.