Was the Eastern Roman Empire really doomed at that time? (Constantine IX's biggest mistake)

While the Eastern Roman Empire at that time during Constantine XI's reign was utterly diminished (only having Constantinople and the Morea), I do wonder if it might have made a miracle revival if given enough time.

Even if the empire had little military power at the time. Just existing made it an effective obstacle for the Ottomans by blocking it's Balkan and Anatolian territories to the point it had two capitals, Edirne and Bursa, respectively.

Constantinople was also an entry point for reinforcements such as crusades from Western Europe and Eastern Europe, forcing the Ottomans to fight an enemy army in the middle of their empire.

The last is that Mehmet II's position isn't stable due to the Turkish tribal nobility limiting his power due to the Ottomans being originally united by several tribes.

Had Constantine XI not made the biggest blunder of threatening Mehmed II to release his political rival, Orhan. He might have prolonged the Eastern Roman Empire's life, but alas, he became the symbol of the Empire's glorious end.