The image of the evil genius serial killer is mostly a Hollywood invention. Real serial killers generally do not possess unique or exceptional intellectual skills. The reality is that most serial killers who have had their IQ tested score between borderline and above average intelligence. This is very consistent with the general population. Contrary to mythology, it is not high intelligence that makes serial killers successful. Instead, it is obsession, meticulous planning and a cold-blooded, often psychopathic personality that enable serial killers to operate over long periods of time without detection.
More realistically, the reason serial killers are so hard to catch, is because it is a crime without any motivation. It coul've been done by anyone. Because it makes no sense.
Not to mention police corruption. Every other true crime episode is about how their first victim walked into a police station with two knives still lodged inside them and the police assuming they're a junkie or something. They literally take people feeding the homeless or picking still sealed food out of grocery store dumpsters more seriously than murders it seems.
I think this has nothing to do with corruption. Okay, how to you catch a criminal who has no logic, or motivation behind his crime. This is why profiling was invented, to try to describe the criminal as a person, because any other method is just doomed. And the truth is a regular officers have no experience in profiling, because profiling is as useless to figure out any other crime, as normal methods are useless to find serial killers. Serial killers are an extremely rare occurrence, which is what makes them so fascinating. They need to be caught by special methods, that most officers are infamiliar with, because it is almost impossbile that they will ever face a serial killer in their career. So if you have a training budget, any other training makes way more sense.