It is no secret that Mark Hamill didn't initially love Luke Skywalker's story in Star Wars: The Last Jedi. Mark Hamill is a huge fan of the Star Wars universe and feels a sense of ownership over Luke Skywalker, so he is going to be skeptical of any deviation from what he envisions for the character. While he eventually came around on The Last Jedi and regretted voicing his doubts, this wasn't the first time that Mark Hamill had some qualms with what the Star Wars film series was doing with his character. He also had issues with the darker direction for Luke in Star Wars: Return of the Jedi, as he explained:
I read [the script for] Jedi and thought, 'Wait a sec! I thought I was heading toward the struggle of heading to the Dark Side. I'm in black. I have a glove. I see a trend here.'
It's funny to think that a version of Luke that is so beloved now, clad in black and wielding a green lightsaber, is something that Mark Hamill had issues with before filming. That version of Luke Skywalker walking into Jabba's palace in a black robe is one of the character's most badass moments. But you can see how all the symbolism might have looked to Hamill at the time. It might have seemed like this character was destined to turn to the dark side. Speaking at the SXSW Film Festival (via ArsTechnica) it is clear that Mark Hamill had a vision and his own ideas for Luke Skywalker in his head, and they hewed closer to the unwaveringly good and hopeful farm boy of A New Hope who was eager to become a Jedi and not someone who was straddling between light and dark.
Apparently, like Anakin Skywalker before him, Mark Hamill is a slow learnerm and he also doubted Rian Johnson's vision just as he once doubted George Lucas'. Rian Johnson's film introduced audiences to a Luke Skywalker different from the farm boy and even the character at the end of Return of the Jedi. The Jedi master had become bitter, cynical, devoid of hope and resigned to death. This was not the Luke we fell in love with and Mark Hamill did not approve. But just as Luke Skywalker didn't give in to the dark side temptation in Return of the Jedi, he didn't give in to despair in The Last Jedi, reigniting hope in the galaxy and changing Mark Hamill's mind. Such is the case with hindsight. Even The Empire Strikes Back, the greatest sequel of all time, had its doubters when it released, but the arc of history is long and perhaps those who don't love The Last Jedi now will come to appreciate it in time.
It is great that Mark Hamill cares as much about Luke Skywalker as the fans do, and he has his own beliefs about what is best for the character and where his story should go. Not all actors feel that kind of attachment to their characters, but it is great when they do. Perhaps if Luke Skywalker returns in Episode IX as a Force ghost, Mark Hamill will finally learn to trust the filmmakers, but if I were J.J. Abrams, I'd be ready to field some complaints.