All I will say is CBS Evening News asked for this ratings drop to happen. The ingracious manner that they dumped Jeff Glor was repulsive, who although may not have the same gravitas as Cronkite or Rather, demonstrated impartiality in his reporting and was very talented. He was one of the few that just anchored the newscast, like old school style. No opinions from him. Just the facts and let the audience decide. They should've stayed with Glor for the long-haul. Yet the ingracious manner they dumped Glor was contrasted by how, on his final night, he decided to honor the people behind the scenes. He could've used that final segment to be about him, but instead he shined the spotlight on the team rarely (if ever) seen on air. That speaks volumes about his character. It's CBSEN's loss that they dumped him.
I won't get into my personal opinions about Norah, but she is not exactly impartial on the air, which is a problem for CBSEN recovering its reputation and ratings. And deciding to move to DC was about as tone-deaf as anything. They should instead be working to re-build their credibility, which may take years to achieve. Getting to say you're live from Washington in a nice studio says nothing about your actual journalism and content.
True that this ratings problem started decades ago, but CBS has the ability to do better. They just have to choose to do better.