I need to explain how giving away Imperial Authority and power to our vassals making them similar to the Feudal vassals of the west so that they will help us with their personal funds and armies weakens us?
Yes, given that we currently have jack shit for authority anyway and de facto power we have is zilch and is loaned by Doukas, mother and church.
We do not magically have power just because we have it in theory; power is a function of who can take it, and if feudalism makes taking it more problematic and less tempting for others it makes us factually
more powerful. I am inclined to trust max's explanation of how this is the case, unless someone presents a compelling argument.
My understanding is that Byzantium's problem was constantly getting nibbled at by everyone around it, not some inherent weakness of its non-feudal nature.
In fact all of those Western nations become centralized and bureaucratic later on, and the faster they did it the faster they rose.
Counterexample: Ivan the Terrible and his attempts to centralize leading to a century of dark times (oprichnina and the like).
Like...centralization - ability to centralize - was, in my understanding, consequence, not cause, of the rise; or at least it was started not by magical foce of will, but by lucky opportunity to counterbalance nobles with somebody else.
In England->GB it was, IIRC, combination of wealth becoming new nobilty and selling positions in administrative apparatus
and rise of yeomenry - rural small businesses more or less, not mere wealthy peasants - as new 'factions' to give king opportunity to throw down with the nobles. If king tried to brute force centralization, well...he wouldn't have stayed king for long, I assume.
So, uh, if you want to claim that centralization was
cause of success, you have to kinda prove it, because to the best of my knowledge it was the other way around, kinda. it's complicated, but certainly not something as simple and, on surface, wrong, as "centralization lead to success".