I think what most people are concerned about when they say content is "dead' is just that it's harder to find people to do it with you.
Like for instance, I would really like to find 3 other people that want to do potd 50-200 with me! But, unless I just want to farm only the low(1-60) floors for experience points, it's not super easy to find anyone. Palace of the Dead does have some items that drop that are worth a hefty amount of gil. There is the mount for instance that sells for about 30mil on my server atm. However, even with a motivation like that, I still haven't seen any pf groups for it in a very long time (well none that fill that I've noticed or joined), nor have my linkshells or fc been interested. I even ask my friends and they aren't motivated to go and say it's not fun for them. I know it's a bit of a time commitment, but not nearly as much as learning some of the high end content. But I'd say the difference is that people don't really care about glamour items and gil as much as they do for actual gear for their characters.
But there is that new cross realm party finder now too with this patch? I guess it probably won't help for aquapolis though since you have to be in the zone for the portal? I'm not sure how that will work.
