Making Obito and Madara juubi jin and turning Madara into Kaguya gave them insane regenerative abilities and with their truth seeking ball they were unstoppable so kishimoto made them lose Preta path somehow and gave them a weaker version that can't absorb senjutsu based attacks, he did that so obito can get the bijuus extracted by cutting him with susanoo sword which has senjutsu from Naruto, and sealing Madara and Kaguya can only be done by the yin-yang seals because they have senjutsu(maybe).