Is categorizing Luke as a symbol of hope and optimism really... correct?
When we last saw Luke in ROTJ he was definitely hopeful and optimistic. He laid it all on the line to give his father a chance to come back and was ultimately rewarded. This is despite him being driven almost entirely by fear throughout Empire. So he's learning and getting better... moving toward the qualities of a Jedi as Yoda taught him.
But Luke is also characterized as struggling to keep from succumbing to the darkness. It's slowly getting to him. We see it throughout Empire and he really walks that line. At the beginning of Jedi he's all in black like Vader with his mechanical hand showing that he's slowly losing that battle. And despite his hope and optimism he very VERY nearly turns. The Dark Side comes SO close to claiming him.
So by the time Johnson shows up, the big decisions have been made for him. Luke started a temple, Snoke got to Ben, the temple burned, and Luke responded by running away. There is no "hope and optimism" version of that.
Han is killed and the Hosnian system is wiped out, and Luke does nothing. There's no "hope and optimism" version of that, either.
There are lots of "fear" and "struggling to keep from succumbing to the darkness" versions of that setup, though. Every decision Johnson made regarding Luke was justified with the events of TFA and Luke's character history.
Added to that, one of the most revered Legends stories ever written was about Luke willingly falling to the Dark Side and serving as the resurrected Emperor's apprentice. That should have served as a pretty good barometer for some of the choices Johnson made (conflicted Luke, Force projection), and I've never understood the vastly different reaction because the "bring Legends back" and "Rian Johnson hates Star Wars" Ven diagrams have a ton of overlap.