I don't think that whether or not you hit should be determined by a RNG; if you point a gun at a person six feet in front of you, the crosshairs are lined up perfectly, and you pull the trigger, you should hit the target, even if you don't have much/any training in the use of firearms. That's not the shooter fan in me talking, that's just how guns (usually) work. That said, I think that the interaction between skill level and gameplay can and should be a lot more complex. On a basic level, skills should be a lot harder to level up, or we should get fewer points to invest overall. Weapons should be locked into tiers a lot harder in regards to skill level. Like, revolvers should be very "easy" to use, semi-automatic pistols should be unlocked next, then hunting, then automatic weapons, all the way up to... whatever would logically be the most difficult weapon to use effectively. Miniguns, maybe?
Gun skill should affect things like sway, frequency of jams (although that might run over with Repair), and reload speed. Maybe your character wouldn't even know to aim down the sights of the weapon until he hit 20 Guns because he learned everything he knows about shooting from 80s action holo-tapes. Fundamentally, I think that the best thing that Bethesda could do would be to make skill level felt, not just displayed through random missed shots when your level's too low.
Peripherally related, I think that it would be cool to add interaction between the different skills. Like I said, maybe your effectiveness at restoring weapons and preventing jams would be determined by a mix of Gun and Repair, or increase chem effectiveness with a formula that accounts for Medicine and Survival. I mean, that sort of thing makes sense, right?