First, Bright Noah does not exist in the Evangelion world. Second, even if they did have their own version of Bright, a lack of a positive environment like in SRW would result in Shinji actually getting worse. Third, getting hit in the face affects people differently. Despite what may happen in the SRW@ continuity, Shinji strikes me as the type of person who doesn't respond well to violence towards him.
I mean, it's fun to think of Shinji becoming a badass after getting a BRIGHT SLAP in the tradition of UC Gundam, but I seriously doubt that the 'real' Shinji would all of a sudden gain an unbreakable spine. Maybe if it happened early in the series when Shinji is just an angsty kid, but he's so depressed that he will probably just chalk it up to "EVERYONE HATES ME!" again. And if it happens later on there's pretty much no hope.
What Shinji needed was a well adjusted person to believe in him and tell him they loved him. The problem was, everyone around him was just as messed up and/or didn't know how to say they loved him.