The Capitulations
The Capitulations were originially trade treaties granting rights to European powers to reward them for being good when the Empire was at its height, and usually granted the power special low tariffs and the right of their citizens to be subject to their own legal system. Thus, if an Englishman committed a crime, he would be tried by an English court - unless of course he committed a crime against an Ottoman.
As time passed and the Ottomans grew weaker in relation to the West, these treaties became more and more an exploitation and seriously hobbled the Ottoman economy, and were a leading cause of resentment; they were also a cause of deteriorating relations with the Christian minorities, who were registering as foreign nationals and thus gaining enormous competitive advantages. This was the primary source of Muslim hostility toward the Armenians, for example, whereas the primary Armenian grievance was that they had to pay their regular taxes, and also "protection money" to Kurdish tribal chieftains, whom the Ottomans had very little control.
All-in-all, the tax burden of Ottomans was far lower than what a Westerner would have to pay, but it is the perception of inequity that causes resentment.
In any case, the removal of the Capitulations would have allowed native Ottoman industry to develop, and this is probably of greater consequence than gaining new territory, although it would certainly be nice to have Azerbaijan and the oil fields of Baku.