I am sure from my understanding that the server is at a limit that it can just about hold, It has already been increased once, which you could tell the difference. Until maybe source 2 comes out, I am sure that the server will stay the slots it is. The gamemode and content and map are a big part of the server, they can just about hold at the slots that are on the server currently.
I completely understand what you are saying, sometimes It is a pain to get into the server, but I generally do what is said above, spam the join button, or try back later. Thing is with how much there is, certain things cannot really hold this. Great suggestion, but it never work until maybe a new engine.