I think what some are getting at is that Luke as a macguffin feels tacked on compared to something like Spock in The Search For Spock. We get the map to get the ball rolling, but SKB takes over the show as the new macguffin halfway through the movie without being set up beforehand. It came across to me as somewhat arbitrary, and didn’t feel like an organic part of the story.
Not sure whether introducing it earlier would help, or tying it more closely into the Luke thread.
SKB is the thing that stuck in my craw the longest coming out of TFA.
Then again, I remember that the Search For Spock also had a tacked on, rehashed doomsday device, didn’t it.

Fascinating.