Q1: Several writers and reviewers have dismissed this song as being below average in the tune department, to which I would say, what are you listening to?
What does "department" mean in this case?
Q2: The way the final bars build and then resolve is a songwriter absolutely on top of his game.
What does "game" mean in this case?
Re: "the tune department" and "on top of his game"
1- We use 'department' colloquially to restrict or define an area, so ere it only means that the tune is dull- the video, lyrics, etc, could be fine
2- Performing well, doing a good job