Ads is aim down sights or scoping in or iron sights. Its a concept that was introduced in modern shooters. I dont even remember it being a thing until i think goldeneye on the n64 had it a little bit and really when i played halo combat evolved on pc when it first came out. But back in the day when i was playing doom and wolfenstein off floppys on my DOS machine there was no such thing. ADS makes it easier to aim honestly slows down combat where this game is meant to be more fast paced with characters that can wallrun, fly and even teleport. If no iron sights is the complaint im going assume you began playing shooters during the yearly COD era? Im which case i can understand it feeling a bit strange and hard to get used to.