Forts need a global cooldown after being captured, otherwise you can just wait for the defenders to leave and cap it. you can do this repeatedly until the defenders give up and no one gets to turn in PvP quests unless theyre ok leaving their fort undefended.
you can literally beat down a group trying to catch your fort, drive them off or kill them all, then as you leave to turn in quests they just cap it again.
put a 1h cooldown. that gives factions time to actually benefit from the fort bonus and means more players will be ready to capture it when the cooldown is about to be done.