I agree with most of this but I never understood the sentiment of the demigods getting weaker, ER isn't like Dark Souls where the bosses we fight are a shadow of their former selves.
Of the demigods we fight, only Radahn and Rennala (she's not a demigod, but still) are the ones who are actually weaker, and radahn doesn't even count after the dlc anyways, since Consort Radahn is undoubtedly his strongest version. Mohg has spent thousands of years building his blood dynasty by the time we encounter him, Malenia blooms once again against us, Morgott unleashes the power of his Omen heritage to stop us, Godrick has been grafting the shit out of himself, Messmer unleashes the abyssal serpent to beat us, Rykard is at his strongest when we kill him and Miquella ascends to full godhood.