Hey there, there's a lot of reasons why the CP server isn't being used lately, and I don't want to start a new long explanation (I've done it already several times somewhere else).
The main reason is the changes Valve made to Quickplay. Valve is now sending all quickplay traffic to their "official servers" instead of giving all community servers their equal chance. I know why they decided to do that (Pinion video ads crashing clients, server admins abuse, etc... etc...), and I don't blame them. Unfortunately, they decided to penalize all communities, even those that respected the Quickplay agreement.
Second reason is there are less and less TF2 players around, while there are still a lot gameservers. It's just more difficult to get a new server started. I think even large established communities are having troubles creating new servers lately.
There are many things we could try, and see if it could boost traffic at least a little bit though. It will be probably impossible to see as much success as the Payload server, but if we could get at least a full server for 4-6 hours a day that would be great.
I believe there's already another thread discussing what we could do for the CP server. Looking at the most popular CP servers out there, I see Instant respawns 24/7 Dustbowl servers at the top. I'm sure it would be a lot easier to capture traffic that way, but there are obvious downside.