Luke has always been a whiny little bitch, at least for all of 4, 5, and part of 6, its in his nature, just like his father who was a whiny little bitch through all of 1,2,3. It seems completely in character for him to be a grumpy ass when he got older as thats just the extension of being a whiny bitch younger in life
That and also going by existing movies and games Jedi seem to have a tenancy toward grumpy isolationism if they don't die (relatively) young.
I liked much of TLJ, and I really liked its Luke. Especially when compared to the Luke of the EU novels and comics.