So many people that take psychology courses end up working in the advertisement industry because that's where the jobs are if you have a psychology degree. Very few people sit back and think about the implications of the scientific study of the mind being used by companies to distort peoples perceptions and make them buy things.
They are literally trying to control our minds. It's not a conspiracy theory this is out in the open public information. If some companies decided to they can make you depressed to sell more things to you and you wouldn't even know it.
Imagine the pick a teenage boy. This boy is a bit shy and insecure. Now, psychology was originally intended to help people. Under the capitalist model it doesn't. Now this teenage boy instead of being recommended stuff to help them will instead be recommended the likes of Andrew Tate and so on. This person won't even know what hit them and won't even understand the turn of events that will lead to those videos being recommended. But they are recommended to him. Suddenly his change in behaviour pushes people away and he falls deeper and deeper into a rabbit hole.
They get more depressed. More lonely so they start buying shit like AI girlfriends but they aren't real. They get recommended more hateful content as well. They will sprial deeper into depression. This person will likely seek help at this point. Perhaps they'll recommend putting effort into real world connections so they download something like tinder. But all these apps are designed to make you pay in order to succeed so he pays to get special access. Now the ad companies know they'll loose money if this now grown man becomes confident so they start recommending content that'll make them more anxious and depressed about the experience. They give up and retreat further into depression. The whole time the person who is being targeted, their family, their therapist and their loved ones will never be able to put the dots together. They'll wonder what went wrong not knowing that their personality was already decided for them by ad companies years ago.
So like that they add companies weaponising human psychology can target a teenage boy and basically plan out the next ten years of their life. Think about how dystopian the weaponisation of psychology is when a family member of yours goes down the alt right pipeline after "suddenly" being recommended such videos.
Outside of products that are themselves addicting, I don't really see any actual harm coming from advertising. Yes, I fucking hate ads, but thats because they are annoying and interrupt the things I do like. The real manipulative practices I see come pretty much from the video game's industry. Alcohol and tobacco are naturally addictive and the people who make and sell those products do rely on that for sales; but the advertising isn't making them more addictive. Games, on the other hand, are true weapons of psychological warfare.
Many development companies have psychologists on staff specifically to come up with new, stronger ways of addicting players or causing FOMO, or otherwise manipulating a small handful of the population susceptible to such a degree, they would go into ruin spending money on useless digital shit. And it's like every little thing in the game. Your eyes are generally watching a game you're enjoying a lot more than a TV ad, billboard, radio advert or other form of advertisement we are constantly bombarded with.
You ever see a video or play Call of Duty and wonder why there is so much "noise" on screen? Why it rewards you for every little thing you do? Because completing goals triggers endorphins. Instead of waiting for a win or loss of an entire game, they can hook you on the good brain chemicals by giving you tons of smaller accomplishments in rapid succession. When games have rarity levels for things you can buy with real cash, things that can literally be created out of thin air if they so desired because it's a piece of software, it's manipulating you into thinking somehow there is some scarcity in a thing that in actuality has none.
They are so good at manipulating the player, they can get you to do things subconsciously just with a few tricks of level design. A lot of this manipulation is just the nature of the beast; but plenty AAA devs weaponize the shit out of it and it's pretty scary that if they wanted to, they could likely "Manchurian Candidate" someone. Though I suppose there is some humor to be found in that violence itself in a game does little to make one violent IRL; but it actually would be possible to design a game that drives the right person to violence, if someone was sadistic enough to make such a game.