They really should have kept this scene in Clone Wars, or at the very least, bring it back in the live-action form as a flashback in the Obi-Wan series. it was sad to see Ahsoka leave the Jedi, but on the bright side, she didn't fall to the Dark side the way Anakin did. And Obi-Wan is right when he says Anakin will never fail him. Even before Anakin gained his iconic Darth Vader suit, but after turning to the Dark side, Obi-Wan says that he failed Anakin, not the other way around. And even Ahsoka felt the same way when she faced her former master in Rebels, she wasn't there for Anakin when he needed her most, so she blames herself just as much as Obi-Wan did, if not more.