Kishimoto restricted Kamui because Naruto and Sasuke were not strong enough. In Madara's case, they obtained the Sage's powers. Pretty sure Obito wouldn't have done well even with Kamui if he went against current Naruto and Sasuke.Unrestricted Obito would have meant the end of Narutoverse. Unrestricted Maddie is a fairy tale, he had access to all his power, he failed to use them properly, unlike Obito who had his Kamui taken away as a JJ just to keep things fair.