Of all the stories I've read of SAS missions in the 90's - the very first thing the soldiers did was dump their SA-80's in favour of the hardy AK. GIs in Vietnam did the same with their M-16s. Some weapons are just crud, and some are epic, it would be less realistic if all weapons svcked just because you're at a low level. It would feel too much like a game. Since Fallout is in a death match with it, I'll mention Assassin's Creed! Like when your character is ignoring the fact that he can do so much more, and yet is waiting for you the player to progress to unlock those abilities (like grabbing out for a ledge when falling). It's dumb. He can do it, but he's not, and it's never explained. Why isn't he? Is Altair so noble he won't break the rules of his master, and reach for a ledge while falling? lol Weak.
How could you explain every weapon in the game-world being 'just powerful enough' to suit the level of your character? It would be weak. NV found a good balance I think. Arming Ranger's with crud just because in the event they die, or you kill them, you the player would have access to whatever they're carrying. Which would be... crud... because you're at a low level. That'd break immersion for me.
As to 'too many weapons', more weapons equals more choice. Choice is great. My first play-through I used the Service Rifle, Sniper Rifle, and a 10mm the entire game. I ignored other weapons, didn't put points into Energy Weapons, and I had a blast. My character didn't look twice at more powerful gear, he was handy with what he knew. S'not all about power gaming, or gimping. When Zulu's kicked the crap out of British Red Coats, they didn't find them all suddenly armed with crappy spears, they picked up the Martini Henry rifles and had a ball using them against the next lot of Brits.