The fact that most people are succeptible to harm *is part* of what makes a weapon dangerous. A knife loses ALL efficiency if we only count krav-maga experts, for example. Swing at them, and they snap your wrist and cave your throat in.
(interestingly, at 3
,5 metres, the krav-maga expert can only try to rush you before you shoot them twice in the chest)
Woulda-shoulda-coulda isn't gonna change the fact that most people are not fighters, they're not very agile or very fast or very strong OR very brave, for that matter. In wars, most people directly affected become refugees - this include healthy men who in theory could have fought, they just don't got the "stuff" for it, they aren't in the armed forces. In hostile and dangerous situations, most people will react from their fear.
Guns are undeniably better than knives. Way, way, wayyyyy better. That's why all law enforcement, all security contractors and all armed forces prefer them. Even the most pacifist gun-restricted countries in the world - like Norway - will do the gun-dance when shit hits the fan, because knives simply won't do. In my military service, I shot guns, because that's what we had. We also had a bayonet and a knife, and not once did we recieve lessons on how to wield these. Rifle drills on the other hand, we did those quite often, and I wasn't even in the proper infantry, but logistics, basically we brought stuff from A to B in trucks