The fact is that Rome's parasitic patrician class was were more interested in maintaining their social position as slave-owning lords of absentee plantations than they were in insuring any sort of agricultural productivity or functioning economy, and the Emperors never had the guts to break them.

Agreed. This was a significant part of the problem but only part. Revenue also declined due to population loss and land going out of cultivation. This got to be such a problem that when the Franks settled in Gaul they could settle on uncultivated land. As to the oppressive exactions of the Empire causing land to go out of cultivation, in North Africa when the Vandals took over a province, land went back into cultivation and prosperity increased. The Vandals had a much less complex and expensive administration. Then when Rome reattached the province the land went back out of cultivation. At least this is what Tainter got from his survey of prior work.

As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."