Not sure the Huns were the biggest direct threat either (unless we think that they are directly responsible for the Gothic migrations/invasions who were the ones who took over significant parts of the empire).
> provinces and basically amounted to plunder.
Also redistribution. The mid/late Roman state spent had huge taxes and spent almost all of it paying for its professional army almost all of which was stationed in the provinces.
As a consequence the Roman economy was highly monetized, long distance trade was widespread and different regions economically interdependent which again seems rather modern.
Also when talking about “plunder” in the ancient world it's almost entirely slaves not gold/silver or moveable goods. That had mostly dried up during the imperial period.