Interesting idea to move the Evening News to a different time slot, but I'm not sure if it would be better. I imagine most people have heard the news of the day by that point, and are more interested in relaxing with entertainment content before bed, rather than news. I wonder what it would be like if primetime across the country moved from 7pm-10pm, local news 10-11pm, then network news at 11pm, with the late shows at 11:30pm?
Anyways, despite whatever reason people may claim is the problem with CBS in the short term, I think it's really much simpler. Do you really think people are not tuning in to CBS because 20 years ago something happened that most people aren't even aware of? I don't think so.
While there may be a few specific reasons CBS Evening News is struggling against its competitors, I think it just comes down to the fact that TV news is slowly dying. Yeah, that sucks for "us" as fans or myself personally, it being my career. But society and culture is changing, and TV news is losing out to other methods to get news and to other ways people want to spend their free time. Some organizations are experimenting (Tegna) to see if there is something they can produce that consumers want....maybe they'll strike gold, but currently I don't see that happening.
Ultimately, I view TV news like a landline phone. Slowly dying. Some people still have one and enjoy it, but others have dropped it and moved on to other options. Then there's others that will never use one because there are better, more attractive, more convenient options (cell phones, internet), so they will never want a landline. Which means there is almost nothing landline providers can do to attract people unless society/culture shifts in some way to prefer landlines again, which doesn't seem likely.