Let me throw my two cents in...Rome fell primarily, because of 3 factors. The 1st was social: Families didn't want to send their "boys" off to war to defend Rome; and the soldiers rather fight for who paid them most, rather than their homeland.
The 2nd was political: Too many leaders were corrupt and interested in their own political gain/money/power instead of their countries.
The 3rd was economic: The barbarians (Huns, etc.) were disrupting trade in the empire...this led to less trade...etc. (I'm oversimplifying it b/c of time)
The Final Nail in the Coffin was Barbarian attacks. The barbarians had the will, not the might. The Romans had the might but not the will.
Sound familiar?
Just Maybe The LESSONS of History are worth something.
Nicely summarized.
There is no doubt too, that the Romans watered down the significance of Roman Citizenship by giving it to those who didn't value it.