UPDATE: It seems that Mark Hamill has addressed this issue himself.
I regret voicing my doubts & insecurities in public. Creative differences are a common element of any project but usually remain private. All I wanted was to make good movie. I got more than that- @rianjohnson made an all-time GREAT one! #HumbledHamill https://t.co/8ujJfBuEdV— @HamillHimself (@HamillHimself) December 26, 2017
Even a casual google search on the Last Jedi reveals things like this story called "Mark Hamill 'still hasn't accepted' Star Wars: The Last Jedi storyline: 'He's not my Luke Skywalker'". This idea was around before the Last Jedi opened, the idea that Mark saw the script from Rian Johnson and immediately thought, "This isn't my Luke Skywalker!" Which is fine, Mark is allowed to feel however he wants about his character. There are plenty of clips from history showing he has always had mixed feelings about the character, even as far back as Empire. The thing is, in my humble opinion, this idea being spread around before the new movie even opened, is what laid the groundwork for the weird reception The Last Jedi has experienced.
Historically middle stories in trilogies tend to have rocky starts. Mashable has a great article on how the Empire Strikes Back was received back when it opened in 1980. I lived thru this and I saw it for myself back then. And I watched as slowly the narrative about Empire started to change. Eventually it became the Holy Grail of the Star Wars Universe, a thing you couldn't touch. Empire was so good comparing other sequels in other franchises to it became cliche.
Star Wars has famously been challenging to many actors. I appreciate that fact. Reading a Star Wars script for the first time has to be weird. And then to find your entire career being defined by a single character doubly so. I get it. There are tons of stories out there about this. Harrison Ford, Alec Guinness, and many more have struggled with this concept in the past. So Mark having issues isn't a surprise. The surprise is just how vocal he has been about it.
Typically this is something that comes out later as an anecdote around the time the DVD is being released. That is how the PR for such news is typically handled, in the commentary, or on the junket tours to promote the digital release after the Box Office run is finished. Frankly I'm surprised that Disney has allowed Mark the ability to spread this story before the movie even came out, but more surprising is that he'd want to. Believe me, I love Mark Hamill and seeing Luke in action again was awesome. I think Last Jedi is the best version of Luke we've ever gotten. And Mark deserves as much credit for his performance as we can give him. But maybe stop with the negative press?
Mark being upset about the direction of the character planted the seed that something was wrong with The Last Jedi before people even had a chance to see it. If someone as revered as Mark Hamill had issues with the movie... well then, something must be wrong with it.
Much like what happened with Empire, those that hate The Last Jedi are on the wrong side of history. Certainly the film has its flaws and I'm not going to say it is perfect because it clearly isn't. But neither is Empire. It just would have been nice to go into Last Jedi without knowing that the beloved actor we all couldn't wait to see in action again - didn't like the way things went with his character.
I love ya Mark. But maybe next time, keep your negative opinions to yourself until after the movie comes out?