What's wrong with ADS? Personally it's leagues better than what halo use to do. And sprint? really? How dated do they want to game to feel?
Exactly the way I feel. The funny thing is, Halo has always had weapons you looked down a scope to help increase accuracy. Sniper rifles, DMRs, battle rifles, rockets launchers, and even pistols. The weapons that didn't use sights were weapons that were really only good for mid to short range engagements anyways. So shooting from the hip was actually a good option and even used in games like Call of Duty and Battlefield. This just gives people who want increased accuracy at ranges where they feel more comfortable to use them the option to do so. People will still very likely fire shotguns and assault rifles off the hip.
Also, the weapon in that clip is a battle rifle. A weapon that had a scope you looked through for long range or fired from the hip at mid range but at that point you were better off using a different weapon. So aiming down with that weapon is actually common anyways. The difference is that apparently weapons in Halo 5 will have attachment options and one of them for the battle rifle is the sight we see in that clip instead of an actual scope. Basically, people are pissed that options for playstyles are being added instead of keeping the game a constant run-n-gun hipfire-fest for pretty much anyone not using a scope weapon that they don't even like. What makes that even more entertaining is that people are crying that they want to keep the run-n-gun feel but they don't want sprint. What?
Like you said, Halo has felt dated. Its mechanics have remained almost entirely unchanged since the original game from 13 years ago.