Incompetence is certainly an issue but I'd say there are a multitude of problems with law enforcement these days, from the lowest patrolman to the feds.
Overpolicing, a pervasive us-vs-them attitude, lack of disciplinary action (i.e. "we investigated ourselves and found no evidence of wrongdoing"), protecting each other to a fault even for serious crimes, severe overreach and lack of "good cops" calling anyone else out on it, etc.