If the 4 admirals turned the first this to go would be Maines hq. Then the gorosei who have to get the report by then the marines and maybe some cp agents might have tried to stop them. Then before the gorosei go to actually stop them multiple agencies would have already tried. It isn't like the gorosei just show up. They are mostly last to every and rely on the branches of the wg to do thier jobs. If gorosei were front and center we would even have yonko as they'd go and take them out when they started. They can go and fight they yonko rn with the admirals and take out yonko after yonko but don't. So yea they'd be last on the scene with the admirals doing alot of damage before they went down.
if the wg get out all his cards to try to obliterate the piracy, yonkos would have no choice to ally between them with all their armies and it would be complicated to beat them, wg can even get obliterated, but the chose to maintain the balance and their secret existence as long they as they cannot ensure 100 % dominance and chance to erase them which is not the case yet " wg are searching for new weapons " the second part of this response is : the yonkos did not ally yet cuz no reason to do that as long as each of one of them can rival the others and the marine cannot guarrantee the win vs even 1 yonko and his army without cheapshots and new weapons
This make it clear ?