>>1880464
Two school of thought when it comes to making FPS is the arcade shooter school of thought and the realistic military shooter school of thought. The former, doesn't really care about realism, you run and shoot with no problem, maybe there is no reloading, so you just continuously shoot, carry 10 weapons, and you can jump all over the place. The emphasis is on speed and power, you run fast and shoot your rocket launcher. Examples of these would be DOOM, Duke Nukem, Quake, Team Fortress 2.
The later school, still allows you to walk and shoot but you have low accuracy, so you can use iron-sights to have high accuracy, but almost zero movement. To still keep things fast, you get a sprint ability, but when you use it you can't shoot. So you have 3 states: run fast but can't shoot, run and sorta shoot, and stand still and shoot. Other differences is limited jumping, limited weapon capacity. They are much slower, and when done well they are more tactical. Examples of these would be Call of Duty and it's clones, Battlefield and maybe Medal of Honor, as I haven't played one of those games in a long time.
Now, it's not a complete binary, and some games exist on a spectrum of these 2 schools, and there are probably more, or at least you can divide them into subcategories(DOOM clones, Build Engine games, Quake clones, Serious Sam). As for Halo, it was more into the arcade shooter school of thought, you ran fast and shoot, you don't loose accuracy from running, and you are already fast so you don't need sprinting. Now sure, it had limited weapon capacity and so on, again not a binary, yet it was still closer to Quake than to Medal of Honor.
As for why it's controversial, in my opinion, it's because it deviated too much from the former school, and into the later, thus betraying it's small but loyal fanbase of 30+ year old dads.
>>1880531
>I'm still unsure why it has a massive bulky bastard blocking the sight picture
It could be possible that they made it so big and bulky to block as much of the screen as possible, to render less, so that the Xbox could have 60FPS. You would probably need some dev interview to confirm this, and one counter-argument would be the existence of small arms, like the pistol. If the game could be rendered fine with just the pistol, then you don't need something bigger just for performance sake.