There was nothing particularly special about map05. I'm not sure when it first got on the radar enough to get into the IDL wad, but I blame myself for letting it become as popular as it did by including it in several season maplists. The WDL has progressively moved away from these types of "DM" CTF maps that really don't have much strategy (map14, the old zdctf18, etc) and I think their replacements have managed to produce much better gameplay.
Map28 really was played out, it dropped out of priv rotation pretty rapidly and then the decision to replace the more well known version with the newer one proved to be unsuccessful.