If you check the steam achievements you'll notice most people don't even actually play much of the game. Right off the bat 1 out of 10 people didn't even finish character creation. Less than half reach level 10. And barely 10% finished the game.
On the road to Novac, there is a scripted event where a handful of Legion recruits (armed only with machetes and spears) attempt to raid a roaming trader (who's backed by armed mercenaries) and a NCR patrol (who are also carrying guns) just so happen to be nearby.
Unsurprisingly, the Legion gets shitstomped into paste. And so, if you played only a few hours of NV, this is one of the few impressions you get from them.
So whenever you hear some mouth breather saying the Legion are retarded cavemen running at machineguns with pointy sticks, there's a very good chance they barely touched the game.