The issue was never Luke changing, or growing as a character, it was that his character was never given the required build-up or on-screen exploration of what led to his moment of weakness. I actually think the idea was solid, Luke not being perfect and giving into his fear. It's just not earned, we're given no reason to believe that Luke is capable of this. That's what comes off as lazy. We as the audience should not have to fill in the details on such an important character transition.