I really get it. I mean Aquapolis is "old" content...and adding new drops to it doesn't make it seem like new content. It's kind of like if they put some rare new minion into Weeping City, even though there is a new 24man going to be out.

This is just the dev's way though. Actually this is not even the only old content they are trying to make relevant in this patch. There is a single line I noticed in the patch notes that I'm sure quite a few people probably didn't pick up on:
New tradable items are available for exchange from Ardolain in Foundation (X:13.0 Y:11.8).

Item ObtainedItem Required
Legendary Clan Mark Log
Centurio Seals x 500
Yup friends, hunts are coming back too... It's the age old "hunts for twines/coats" thing again....probably.... yay?

I'm not even mad or sad about this. I totally expected it...but ya it's a bit mundane as it's the same things we've been doing the last three years...

Oh yea, and we get to farm light again on our relics... Gonna be going back to Titan hard mode and stuff cause there will be a light bonus there... so yea the lvl50 primals are probably going to be relevant again too.

It's just the way this game always plays out. They even updated the Triple Triad tournaments and stuff so maybe people will actually care about farming cards again...from old content? I doubt Triple Triad is coming back even if they fixed it so people can't "cheat" at the Tournament. It's kind of too late now. The gold saucer is pretty dead on my server so I doubt this will fix that.