After a clip out of bounds by the area where you kill the last moblin, you can fly towards the sanctum from out of bounds and land on top of the area where you fight ganon. With a skew/ advanced skew clip you could possibly get inside, and if you did it could possibly skip the blights and go straight to the Ganon fight? Just a theory, but could work

Someone who is actually good at clipping please try this out

Calamity Ganon doesnt spawn unless every blights have been defeated and there is no way to progress the game once youre inside sadly