That's something I was thinking as well. Usually around this time (within the last months) is when the game is supposed to be "dead" because it's the end of an expansion, but it's the complete opposite with many more people yet to come back or start playing. I guess all the advertising is working, but it kinda seems like there's not enough space for the people.
The active population is 30-35% at level cap right now, and it hasnt increased for 6+ months.

If people were coming back, we would see an uptick, which is potentially worrying both for short term stability and for long-term sustainability, especially on the smallest datacenters.

When you go from preferred to congested, but you still have the same number of people having reached Shinryu and then 4.1 content as you did more than half a year ago, its worrying. You're trading off long term investment for a lot of free trial players, with incredibly low retention rates.