Luke being reluctant is fine and I was okay with the hermit in exile thing, but never to completely give up hope and go off to die alone on an island. TFA felt like it was pointing in a definite direction, and TLJ felt like it was acknowledging that direction and purposefully going the other way (Johnson says as much in pretty much every interview about it: “subverting expectations”) while staring you dead in the eye like a cat pushing a priceless Ming vase off of a high shelf.
I legitimately don’t know how you can think that TFA was “pushing Luke in a definite direction” that somehow excluded his interpretation in TLJ. Genuinely curious to hear thoughts on this, as I truly can’t think of anything in TFA that contradicts his portrayal in TLJ or suggests it would have been something else.
As for “subverting expectations,” I think people read to much into that to mean Johnson was trying to annoy fans at every turn or something. I think what he actually means is more in the minutiae of the telling of his film itself, feinting one way and going another - not to annoy fans but to thrill them with a story that keeps you guessing.
My impression of Luke’s mindset from watching only TFA was that he became discouraged with his effectiveness as a teacher and went in search of something that would make him better able to pass on what he had learned. Since he was the last of the Jedi, the only thing remaining would apparently be these texts on a half-mystical island. Keep in mind that he gave the coordinates to R2 before he left, so it’s not like he went there to hide, at least not in the beginning. There’s also the fact that JJ wanted Luke to be practicing Force techniques when Rey found him.
So the idea of Luke in TFA was that of Rocky having lost a fight and needing to train harder for the next one.
Luke in TLJ has lost all hope.
It’s a not insignificant difference.