Yep, I also don't believe in profiles and profilers anymore, I used to years ago, but they are only good for movies and they only ever solve crimes in movies. Most profiles are very similar as well. As far as serial killers go, like you said, apart from the few that are schizophrenic/psychotic, they are always psychopaths. Which means they have a different brain than the rest of us. They don't feel anything, they have no remorse, no compassion and they just kill because they are pure evil. And that's their only motive, that they are pure evil and just want to make people suffer and see them die.
Also, in my opinion, trying to find out what happened to them in their childhood means nothing. Whatever it was, a lot of people have horrible childhoods and never even steal gum at the grocery store. It's their psychopathic brain that makes them the way they are. And most of them who talk about their horrible childhoods are probably lying as well - a) because they are pathological liars and b) because they always want pity and compassion from other people and use sob stories to manipulate people. It usually makes me quite angry when I see profilers or forensic psychologists and psychiatrists listen to them and believe every word those monsters say about their horrible childhood and horrible life. They should know that it is most likely just a manipulative tactic instead of using it as a base to profile them and to profile future serial killers. They shouldn't let the monsters manipulate them, it's part of their job to know that that's what they are doing.