Halo 4's/ Modern Weapons

In the halo franchise there are numerous Human Weapons. Few of them seem to actually seem to fill the feeling of “futuristic” such as the spartan laser and rail gun, while others seem to be less advanced than modern technology.Personally I feel that the weapons fit perfectly with the timeline because I look at them in a perspective that they’re much more powerful than modern weapons. Many others seem to be bothered with the idea that the weapons are less advanced with modern technology. Example is the shotgun; The UNSC shotgun in halo 4 is a 6 round pump action weapon. This is one of the things I have a problem with. I feel that the shotgun is very powerful and it looks futuristic but it seems to lack something about it. I know that it is for balancing reasons in multiplayer but why by the year 2558( I think) the UNSC doesn’t have a fully automatic shotgun that is loaded with a magazine? Do any of you guys feel this way about the weapons and what is your perspective?