When aiming down the sights of a gun in a game, the only way to aim at another target is to scan the arena while aiming down the sights of the gun, physically moving your entire body... arms, legs, head, etc. This is not how you would do it in real life, where you can scan the arena using your eyes, but keep your head fixed and in a position to continue looking down the sights.
So, there are two ways to respond to this...
One is to agree, and to say that it'd be great if a game came along that had a new mechanism for shooting, because TPS or FPS, ADS or reticule or however they handle it, our games are not really much like what handling a weapon is like. I think adding more authenticity (even if they had to add more artificial mechanics to pull it off) might make for a fun new variation in a game. Taking cues from reality has made video games more fun time after time.
But the second way is to point out that video games are first and foremost "games", they are their own thing with their own methods and rulesets. They do not ape reality so much as they substitute a reality of their own. And ADS, despite the reasons it is hated by some (I'm not sure I understand it myself; some graphics above do show how ADS has been done
badly and maybe this thread could explain a bit further,) it so far has succeeded as a way of adding accuracy and challenge and "realism" and visual appeal to the shooting experience all at the same time. It may not be the ultimate means of targeting in a shooter, but it has so far worked and been received well in the types of shooters we are interested in right now.
Modern FPS punish movement and shooting. They reward the Aim Down Sight mechanic because they have built it this way.
Well, life punishes movement and shooting, but again, two ways of looking at that: reality versus gaming reality. We had shooters in the past that were masterful presentations of gaming reality, and now even games of that era have been affected by the ADS trend.
And I liked your breakdown of Titanfall, how it should maybe have dropped movement punishment because the frenetic kineticism is the reason why Titanfall exists at all.