Deviations... from his character?
You mean the one who whined all the time, so much it was a oft commented on at the time? Or the one who quit trying after he failed to lift the X-wing? Or the one that gave into the dark side and maimed his father, the one he was trying to save, before pulling back at the end, you know, after the moment of weaknes?
Goodness, I have no idea where this concept of Luke you guys seem to have came from (maybe the books?), but the actions Luke takes in the OT are not those of the hero you seem to idolize.
My take on Luke is that his whole character arc of the the original series is from hot headed whiny farm boy to jedi knight. That is the whole point/core of that series for me. So I see some tension between The Return if the Jedi Luke and the Last Jedi Luke that needed far more explanation.
I think that is why so many people are up in arms (but I also think the dropped story lines from the Force Awakens is another whole suite of problems).
It seems to me that there is so much interesting stuff here happening off screen/between the films with Luke's dissolution as a Jedi/ Knights of Rhen/the rise of the First order visa vi the republic, and what we do see in the Last Jedi is just not a tedious side note to this interesting stuff.