The wording in TFA is vague enough that I can come up with a number of other explanations for why Luke is still gone.
It wasn't just in the opening crawl though.
Han flat out tells Finn and Rey in The Force Awakens: " He was training a new generation of Jedi. There was nobody else left to do it, so he took the burden on himself. Everything was going great, until... one boy, an apprentice, turned against him, destroyed it all. Luke felt responsible. He just walked away from everything."
There's not much ambiguity there. Did people just not listen to Han's story? He spells it out pretty clearly.
Luke left everything behind because a student of his destroyed it. Rian Johnson picked up that thread, because it's not like he could ignore it. I mean, I guess he could, but that would be shitty writing, and poor characterization of Luke.
I'd like to know what people expected of Luke Skywalker in this new trilogy. That he'd just show up with a laser sword and take on the whole First Order, I imagine.
Rian made Luke a much more layered and 3 dimensional character. I love that. Yeah, there was shell shock from our idealistic image of Luke Skywalker (which RJ smartly works into the story by having Rey be the audience surrogate in terms of her expectation of Luke Skywalker vs the reality). It's a simple "never meet your heroes," but in the end, Luke does become that idealized version that fan girl Rey, and fandom audiences expected to see. It was just done in a more nuanced and satisfying way than a generic as fuck Starkiller Force Unleashed style display of mastery.
Seeing Luke at his lowest point, then triumphing over his demons and guilt is heroic as fuck. It's what makes characters like Peter Parker so fun to watch/read about. Yes, they possess incredible power, but it's their humanity that makes us love them and care about their struggles.
TFA should have prepared us for Luke in TLJ, and in my opinion it did. Han's explanation to Rey and Finn had me more than curious to see how Luke would be portrayed in episode 8 (I knew he wasn't going to show up until the end of TFA, since this trilogy isn't about the old cast, and the opening crawl flat out stated that the thrust of the movie was going to be finding Luke, and that they weren't going to do that at the halfway point of the movie).
This whole trilogy has been great for me, but TLJ is probably my favorite, warts and all. It's handling of Luke though, is one of my favorite elements of the movie. He was still the same Luke to me, just viewed through a different lens. I dug it.
