To understand what people mean when they say "the server is dying" you have to look at trends that go farther back than just a few months you have posted. (See Sundae's post for a longer timeline of the player rates, there has been a steady decline for the past year)
Naturally games that are played by school age people are going to be less popular during the school year. Over the past 5 years, the server always sees a slight dip at the end of the summer. However, if you look at the past few years of data, there have been very broad swings of the amounts of players. When Kiri first came back as the server manager for Stan and all the staff were banned and the all the chests of the server deleted, the server struggled to get 20 people online at a time (This was 3 or 4 years ago, my freshman year at college when I played as a normal player. A lot of people quit, including my best friend because they were so upset at the drama and their stuff going missing).
But during my time as a staff member, the server really rebounded, we went from barely getting 15-20 players online, to averaging 50 or more for most of the day with peaks of over 100 players. My favorite statistic to look at was how many people were online in the middle of the night EST time, because most of our player base was US kids who would be asleep at that time, it gave me a chance to see how the server had grown. It went from having 1-3 people online from 1am-5am EST to having 20-30 people online at that time. Whenever I join these days, it really does remind me of the times a few years ago when everyone quit...
I personally think the biggest problem facing the "the server is dying" thing is the fact that cities has a very low retention rate. We have soooo many people join, but not many stick around for longer than a week or month. Recently people have been leaving at a faster rate, and that's why we're seeing so many people say the server is dying. Because in the long run, there have been less people online than the peak times a year or so ago. But the server isn't dead, and it wont be dead for as long as there are still people who love and care for it. But it would help to address the issues that people say when they leave the server, because player retention is an important part of a successful server.
Side note: staff cant do anything about the player rates besides being friendly and making a positive environment for players. Even admins like Sundae really can't do much for the big picture. Over the life of the server most players agreed that the staff members as a whole were friendly people who got them to stay longer than they would have normally from being upset about other issues (Based on the responses from the feedback survey I held a few months before I left the server).
