To address your what if scenario, if hacks are changed enough to be like a normal person playing then they might just end up being no better then a normal peron.
not an if, and the performance is still enough to dominate.
i played on a tf2 server a couple of months ago. two guys were talking in chat: stuff about alt accounts with "darktower" or something. he was making tons of headshots with sniper, even on rocket and stickyjumpers flying across the screen. when someone finally sniped him back he accused the guy of 'finally turning on the autotrigger'.
when i specced him, he switched to scout to avoid showing the wall hack effect(shooting at enemy despite obstruction in the way). with his medic buddy overhealing him, using auto-trigger and auto-tracking after he got the crosshairs over the enemy, he was able to go on 12-20 oerson killstreaks despite no massively obvious aimbot snapping. he may have even had a double jump script that triggered anytime someone got lock on him.
tf2 is generally an outside case as only a few classes really benefit from enhanced aim due to slower projectile speeds and damage falloff making instagibs less common.
but the techniques i saw the hack user implementing made it less obvious than you think(especially if you dont know what to look for).