ballistic weaponry being treated as ineffective simply because it’s “old” technology

I mean, from a supply chain perspective, it's much nicer to have a weapon that never runs out of ammo and has very few moving parts, especially when you're deep in the field.

Idk if I'd say the problem is that they're "old" so much as they're "solved" (various scifi alien shields tend to be great at blocking ballistics).

And I think that's supposed to go to the existential horror of alien civilizations. Not that guns, specifically, are ineffective. But that humans feel impotent in the face of foreign invasion.

The movie Alien 2 makes firearms ineffective with wave attacks of alien drones running the Marines out of ammunition, for instance. And more primitive weapons like knives and short range explosives risk throwing acid blood back at your face. They're very effective at first, but increasingly useless as the fight drags on.