Fighters like Thiago Silva, Rampage and others will always have a problem with those who game plan. The octagon is so large that fleet of foot fighters can refuse to engage with the Thiago Silva's of the world and basically run circles around them.
This is an effective strategy in dealing with legitimate badasses who do not bring their track shoes into the cage. If the octagon was smaller the Rampages and Silva's of the world would likely be at the top of the pack. It would be a different ball game entirely.
We saw what happened to Feijao when he decided to actually fight Thiago Silva. The same thing would happen to many fighters should they choose to engage rather than kickbox or run around the cage.