How important is the corpse in detective fiction?

I just read a quote from mystery writer Ross MacDonald who said, “The detective isn’t your main character, and neither is your villain. The main character is the corpse. The detective’s job is to seek justice for the corpse. It’s the corpse’s story, first and foremost.”

Makes you think, this quote. But and I say but, the corpse is certainly the source of the drive to find justice for an injustice. After all killing anyone is the greatest evil we envision, but if left to the corpse, nothing would be solved. The corpse is dead. The corpse may be such an overwelming figure, political or pop culture or scientist or do gooder that finding the killer may be so much less significant than the loss we suffer from the death. We may mourn the dead and revisit their lives, but, again but, the story would stay there until the wrongdoer, the killer, who wronged the corpse is discovered. The corpse, despite all our empathy for him or her, is the catalyst for the protagonist/s to overcome all the impediments to understanding the killer’s motive, methodology in killing, and interpreting evidence to uncover the killer. But, again but, the corpse cannot pound the pavement, interpret witness statements, chase the bad guy, work within the law, and finally ensnare the culprit.

Let’s agree with MacDonald that the story is the corpse’s story, but the main characters are the good guy and the bad guy with the good guy and or his team hopefully prevailing.