In Warzone the map is huge, and 150 players are split up in to competing squads of 1-4 players. So it becomes very much an information heavy game. Knowing where people are, even when they're hundreds of meters away, is extremely valuable, and that's one of the hacks people have. They see nametags, hitboxes and information for players overlaid on their screen. They also change colour based on if they're in line-of-sight, so you can say "I see that squad, but they can't shoot at me, so I am safe" and that's extremely valuable.
Second to that, they can use aim-assist but the highest-end aimbots are really quite nuanced, and they allow you to smooth out the assisted movements and only auto-aim in specific scenarios, and that makes it really hard to tell they're using an aimbot. It just looks like a really good player. Gone are the "snap to head" aimbots of Counter Strike that were so obvious.
You can report someone all-day-long and they may never get banned because the hack software is competent, and it's hard to demark the difference between "Knowledge you shouldn't be able to have" and "Intuition of a good player".