Are we served as a society by the Exclusionary Rule?

Consider the Exclusionary Rule in the large and small picture. There is a homicide of a child and the perpetrator is arrested and charged. The main evidence [does not matter what it is but consider it vital like the murder weapon] against them was illegally obtained. The Court rules to suppress this vital evidence. Without this evidence, the prosecution’s case falls apart and they cannot prosecute. Ergo: The Child murderer goes free. Are we served as a society by the Exclusionary Rule? How do we reconcile this seemingly unjust result? etc.