It's less about the spawn system and more about how easy they are to farm because the small maps make it predictable. There is nothing the spawn system can do to keep you safe if 90% of the map is a constantly rotating combat zone. Like the locker room spawn trap on Dead Cliffs, or the B-Flag spawn trap on Burnout. You have to remember that most of these maps were not meant for 6v6. That was an addition that came later, and the maps were hastily made to support it.