Why is "fan service" a bad thing?

Rating: 9/10 (21 December 2019)

After reading a few reviews, I felt compelled to create an account to just write this.
This was by far the best of the new trilogy. The common criticism I read is that it pays to much "fan service"as if fan service was a bad thing. If my eyes rolled anymore, they'd detach from their socket.
After 42 years, this movie brought back nostalgia, paid off several story threads, and provided a compelling ending. I'm not sure what else you could want? I honestly feel like people (critics especially) went into it wanting to be disappointed.