I think you love the character and wanted to see more than him. That's perfectly fine. You didn't want him to die.
But I went into this movie expecting almost exactly what we got because of how TFA ended. He died a hero, which should at least be of comfort. Maybe it's because I don't over think some of these things, but I looked at the character of Luke Skywalker and thought, "How much longer do you realistically keep him around?" It's not that Mark Hamill is a dinosaur, but how believable is at a certain point if you kept Luke alive through this trilogy and then he came back in his what, 70's?
After a certain point, it gets to where you are beyond believability for a character to continue to exist.