Most of us would agree that Disfellowshipping™ is an overly harsh punishment.
Even when a criminal is in jail, segregated from the rest of society, the government allows for that person to receive training to allow them the opportunity to return to some kind of normal life when they are released or paroled. When paroled, the person has a support system - he has to check in with his parole officer, he has to report to work, and abide by conditions placed upon him (no drugs, alcohol or weapons, and no contact with former associates). It isn't always successful, but for the person who really wants to reform and change his life for the better, this structure can be helpful.
Being DFd is more like being stuck out in the middle of the ocean without even water wings, and being told they have to swim to shore, through storms, frigid water, and constant struggling. The Elders™ are waiting on shore to make sure that the person dog paddles only - no breast stroke, no butterfly stroke, just dog paddle. The family and friends they had can't help them - they have to wait for the Elders'™ approval of the way they dog paddle to shore. Some people don't make it. They get taken by storms. Some just give up. And some come across kindly strangers who are willing to give them the help they need, that the Elders™ won't allow them to have. People with boats and life preservers and floatation devices, that give them hope and show them that life doesn't have to be like this, there are other options.