As much as I love reading Gibbon, I think all this declining and falling is overrated and I find placing the blame on the Tetrarchy, instituted by Diocletian in 293, to be a red herring. It is often used by historians as the beginning of the end. It makes a convenient starting point for a narrative about the start of the “Byzantine” empire or of the “Fall of Rome” but both these stories have always felt artificial, misdirected and misleading.
I suppose if you have to have a Roman Empire you have to have it “Fall” at some point since eventually there is not really anything Roman about it anymore. But I don’t think it was all that Roman in the first place. Let me propose a different narrative (to follow).