He has the Rinnegan still.
That attack naruto/sasuke just used...
Couldn't he just absorb that. One of the Paths.
I don't think he can absorb the attack after he's been hit by it. It's doing damage to him now in the chest, most times we've seen Rinnegan absorbtion it's been through the hands.
A better question would be, why isn't he using Kamui to avoid the attack? We know he can use Kamui to escape from amaterasu (he did it with Itachi's technique).
Despite having the Rinnegan, the only technique from it that we've seen Obito use is the 6-paths technique with the jinchuuriki zombies. He hasn't used absorbtion, soul-nonsense, shinra tensei, chibaku tensei, the mechanical stuff or any of the other cool rinnegan techniques. Maybe he can't do these things with only one eye?
We know that the "true power" of eyes comes when you have both. Maybe the 6-paths technique is the only one he can use with just a single rinnegan.
BUT, we KNOW he can do Kamui with only one eye. He's been doing it the entire manga. After he came back from his dimension fighting with Kakashi he hasn't used Kamui at all. His speed and defenses are so high right now that maybe he doesn't need it and has been overconfidently not using it.