Thats what they want us to think. Akatosh sure kicked Mehrunes ass good. And he was strong enough to keep him out of tamriel for good. Cant be that weak, probably just dont want to communicate.
Or maybe, the Aedra simply have more foresight. And understand direct intervention with a Deity probably wouldn't have the affect. Like the idea of Kyne making a breeze knock someone down a cliff disheveling the rocks along it, why? Because perhaps in a hundred years those rocks will block a path of an already late courier making it so his important order to some Captain doesn't get there on time making it so that his is Agitated and his sight is clouded and loses a battle. Or hits a soldier/Serving girl in his anger, making them spiteful and become a spy.
Its cause you have plot armor its the only reason why they don't wipe you off the map for defiling their shrines daedra princes take the defiling of their shrines seriously I mean REALLY seriously. The whole point of molag bal quest was that a priest of boethiah defiled a small shrine of his and for it bal is most likely going to [censored]/torture him for eternity.
I mean nocturnal messed over the thieves guild and ruined their business because of mercer messing around with something that belongs to her.
edit: I haven't played morrowind is the Nerevarine a champion of Azura?
His sphere of influence is Domination. Power. Control. He sees the world from one lens, and thats that of needing to control mortals saying that makes him evil is like saying the Wolf eating the weak little Faun is. It's simply what there meant to do and they can't see any other alternative.