So, the Ottomans.
On the one hand, they held onto Belgrade until 1867, and managed to make a good go of it as late as the Great War. On the other hand, it's hard not to feel like they underperformed; they fell behind their western names technologically, they didn't adop tthe printing press for centuries, etc. You see a lot of great ideas; a Suez canal, a Volga-Don canal, Ottoman naval assaults on Diu, etc, but none of these happened due to institutional inertia.
How can we get an Ottoman Empire that keeps up with the west?