T
they will not bother too much until Nika leads a force that can actually challenge them.
WG can not or does not take over the world because of the Ancient Weapons. They are still out there and WG fears them.
They probably have one of them, but could not use it until the invention of a proper power source.
Currently we think that the WG is almighty and rules the planet. This is what is being said.
But...
Revos managed to free entire countries and grow ever stronger. And they are not even active for that long. Meaning the WG has less control than we perceive.
We only see the story from their side right now. We never get to see the strength of the opposition.
Luffy will break an 800 year stalemate.