That’s kind of the point though. Luke is worried he’ll make the same mistake he made with Vader, so he exiles himself to Ach-To. But Yoda convinces him to learn from his mistakes, that past actions don’t define you. Luke thinks he’s regressing, but he realizes that he isn’t. Han being a smuggler in TFA was a true regression, since it was only done to make Han more recognizable to the audience. Luke’s arc in TLJ seems like a regression, but it actually serves a storytelling purpose.