A lot of fans had a lot of issues with Star Wars: The Last Jedi and whether or not you agree with them, some of the problems that fans had were at least understandable. Mark Hamill certainly understands most of the questions, except one. While even Mark Hamill shared some of the trepidation about Luke Skywalker's character arc, he says he didn't get the fans frustration with the death of Supreme Leader Snoke. The actor seems to agree with director Rian Johnson's assessment that taking out Snoke allows for a cleaner confrontation between Kylo Ren and Rey in Star Wars; Episode IX. According to Hamill...
While most of the questions that fans had coming out of Star Wars: The Force Awakens were focused on Rey's lineage or what exactly had happened to Luke Skywalker, there was no shortage of interest in Supreme Leader Snoke. Here was a powerful Force user who had turned Ben Solo against his family that, from the perspective of the audience, had seemingly come from nowhere. People wanted to know his story. Not only did Star Wars: The Last Jedi not provide answers, they killed him off without giving them, implying that we may never get them.
It's absolutely true that removing Supreme Leader Snoke from the equation does make for a much cleaner conflict for Star Wars: Episode IX. Kylo Ren, the more interesting character, is now the main antagonist, and Snoke was used to make Ren a stronger villain, so he did serve a purpose.
It's also still possible that Star Wars: Episode IX will explain Snoke's origin. We could still get answers through Kylo Ren. If Ren continues to use Snoke's base of operations or decides to follow through on the Supreme Leader's ultimate plans for the First Order, it could still give us insight into the character without him needing to be around.
Of course, it's also possible that there will be no answers because they're just not important. While there is a mystery surrounding Snoke, that mystery seems to exist solely for the audience, not the characters. Nobody in either of the new Star Wars movies seems to be asking who Snoke is or what he wants. It seems that they know already. They haven't discussed it on screen, likely because it's such common knowledge within the Star Wars universe that nobody needs to talk about it.
Mark Hamill tells GamesRadar Snoke just isn't important. Whether or not that was true once, it certainly is now. We'll see the important characters take on each other in a final confrontation when Star Wars: Episode IX debuts in December 2019.