I always beat this particular Tauntaun but I think the Force went off the rails in ROTJ. Yes, in TESB Yoda was a moralising grouch, but that didn’t necessarily give him the final word. Gary Kurtz indicated that the original story idea for ROTJ would have had Luke wandering off into the sunset via a bittersweet ending. To me that indicates a possible sense of ambiguity for Luke - perhaps a blurring of the divide between the so-called Light and Dark. In ROTJ a simple loss of temper is a path to eternal damnation, which I think is childish. ROTJ also added the genetic component (via the ludicrous shoehorning of Leia into the ‘other hope’ role) which in turn led to Midichlorians and virgin births. The Force was, in Lucas’ words back in the day, “space-Yoga”, and could easily have transcended Yoda’s take on things after TESB.
I believe it was bittersweet because the triumvirate of Luke, Han, and Leia were going to split up. Han dies, Leia becomes leader of the New Republic, and Luke goes off to create a New Jedi Order. But there is nothing to indicate that Luke’s Jedi would be taught a new take on The Force. And again the idea that anger leads to the darkside is first made explicit in TESB, not ROTJ.