Considering that Athens was a classical city of learning and commerce, it's current status in game doesn't really reflect that. It could have an estuary or a center of trade, and it doesn't have much base tax by European standards and it doesn't necessarily have to go to the ottomans.
I know on that last one it sounds like I'm smokin da crack pipe, but the rest are serious. I would concede that by global standards it has high base tax. But controlling Athens means controlling the Agean sea, which is a considerable avenue of wealth at this time. All the shipping wealth of istambul - where is that flowing past? Certainly not upstream into the Crimea.
Honestly though, Athens could easily end up in Byzantine, Venetian, or (on the outside chance) Achean or Morean hands. Playing as a Greek nation against the Ottomans, owning Athens should unlock a decision outright, like getting Constantinople is for the Turks. +1 Base tax, tradepower etc.
A step on the way to forming Greece, if you will.