Mehmed II strength isn't tactics, it's logistics able to muster and sustain the siege. On the siege itself they have to wait for cannons to break Roman walls, other attempts to scale or bypass the walls were defeated. They had up to 10 to 1 manpower advantage. Despite that they still lost roughly equal or more numbers to the defenders.
Anatolia and Thracia was and still rough terrain to move around, despite seljuks superior mobility it wasn't easy moving food and arms. Although by the time of siege Byzantines have lost capacity to do guerilla warfare (4th Crusade basically destroyed Byzantines hold on Anatolian and Thracian despots making it easy to seljuks overwhelming them one by one, also good old fashioned religious dispute delayed and reduced Catholics assistance)