I mean, it’s incredibly exaggerated, but there are plenty of stories of police missing clues that afterwards seem kind of obvious. But it’s a lot of hindsight bias
Except for Dalmer. They found his 14yo victim naked with a hole drilled into his head wondering outside of Dalmer's apartment and didn't even find it suspicious enough to keep them from helping Dalmer get the kid back into his apartment despite Dalmer having been convicted of sexually abusing the victim's 13yo brother and being in parole for that crime.
The were fired about 2 months after the incident when Dalmer was caught after another of his victims escaped. That was in 91, they were reinstated with backpay in 94. One didn't go back to the Milwaukee PD because he was employed by another police agency, the other went on to become president of the Milwaukee Police Union and retired in 2017. They both continue to say they did nothing wrong and that there was no reason to be suspicious. The naked bleeding kid was unable to respond to any of their questions, the neighbors that found the kid and called the police disputed Dalmer's story, the decomposing corpse of another victim was in Dalmer's bedroom when the police returned the kid to Dalmer's door, and the officers made homophobic and racist comments in regards to the incident, the victim was Laotian, but apparently it was unfair to judge them while having the benefit of hindsight.
Even if it is, they're conveniently skipping over the fact that even I their own untrue version of events, they still spent their life in prison after being caught (also pretty sure they don't let you fuck "fans" through the bars in prison, but hey - I'm no expert)