You may not be far off the mark. See "The Roman Empire and Its Germanic Peoples" by Herwig Wolfram. He points out that the Western Empire (which fell over a thousand years earlier) had a far greater disparity of income than the Eastern Empire, and that this meant they couldn't raise the taxes necessary to defend themselves. The Eastern Empire spent a third of their budget on their army, and this was more than the Western Empire collected in taxes. He also points out that this doomed Ostrogothic Italy.

However, the thing that's missing from this analysis is that the Senatorial families that Wolfram is talking about as the super-wealthy weren't just family businesses. They were the equivalent of major corporations of their day. They were huge profit-seeking enterprises, owning sometimes tens of thousands of slaves and having thousands of freed slaves attached. Some of these had annual budgets that were as much as a third of what the Western Empire would collect in taxes in the same period.

We are headed down the same road, I think.