I have to disagree with the sentiment that if Mark Hamill thinks there's something wrong with the character, then that means there is demonstrably something wrong with the character.
Mark Hamill is simply an actor who portrays the character based on how he's directed/told to portray him, and does a good job at it. Just because he portrays the character doesn't necessarily mean his views and his opinion on the character inherently mean it's the right or wrong thing.
Same principle as movie critics. Just because they're movie critics, doesn't mean that their opinion on the a film is somehow more "right" than yours. You both watched the same film. They have an opinion on it, you have an opinion on it.
Hamill himself at the end of many of his interviews, said that he personally disagrees with the direction of the character, but that he hopes that there are people who do like it. I think he's in the camp where it's just simply a shock to see Luke go from RotJ (the last time we saw him on screen), to how he is in TFA and TLJ. Once the shock kind of wears off and what happened starts settling in, I think there are some people (perhaps even Hamill himself) who will come to terms with how Luke was portrayed and realize that how he ended up being later in life, isn't all that shocking after all.
