IMO it's really a combination; scent, movement, contrast and contour.
Scent: even though you can't smell yourself or even if you use the most expensive scent blocker, there are still traces of human scent by which animals can detect. The 'scent blocker' soap, shampoo, spray and clothing does not make you 100% odorless. Not to mention you could spray down and wear these clothes and bath, etc. If you are in the field and sweating, you are putting off a scent, and not only that any trace of scent you put on your equipment, bows, arrows, backpack, etc. can be detectable by game. The best thing to do is to have a general idea of where game will be approaching and play the wind. Have the wind blowing your scent opposite of where game may be approaching, and not blowing your scent to them. I always pretend that even though I believe I am scentless, that I just got done working out, haven't taken a bath in two weeks and am going hunting
I set up to where my stink isn't blown into the games faces
Movement: most game animals are keen to focus on movement. You can have the best camo in the woods and still be spotted if you are moving in the slightest. The best bet is to move S-L-O-W, or in opportunistic moments (such as when game isn't looking at you) draw your bow slow, walk slow (when stalking or moving to and from stands), and while in your set up look around slowly and be cautious of sudden jerks (I am famous for this when I hear a noise). When a game animal is looking at me, I absolutely freeze, I avoid eye contact (I believe they can tell when you are looking at them) and slow my breathing.
Contrast: Although the majority of the game we hunt are considered 'color-blind' they view the world in what's known as grey-scale by which they see different variations of blacks, greys and whites which represent what we see in color. This is why most camos are patterned in your environmental colors of browns, greens, blacks, greys and whites. The best camo to have is one which blends in with the environment, for instance a woodland camo does no good on a savanna, or in the snow. Go to your spot where you sit and take notes of the colors in your area (even better behind you while you sit) and try to blend into the background.
Contour: So you've covered yourself with scentless stuff, played the wind smartly, standing as still as a statue, have camo that blends in greatly with the colors and contrasts of the environment, but however, unless you don't break up your outline, you will still be spotted. Over the countless years of being hunted by man, game animals know when something isn't right, if it looks like a man, it must be a man. You don't necessarily need to go over excessive with the ghillie, but you do need to break up that 'human' look.
These are the major factors which contribute to our success in the field. And what amazes me is how every game animal seems to have different personalities and different perceptions of their environment. I've had instances where one deer doesn't even see me, smell me or anything and then have another deer right next to it spot me in an instance! You may fool some game, but not all. You may fool an immature or young doe, but it'll be tougher to fool a wise old buck!
Do your best to blend in and maximize your advantages involving these 4 factors (I am sure there are more that I lament to mention) and you will find success!
Sorry for the lengthy post!