Shemittat kesafim does not absolve the debtor of his debt. It simply reverses the valence of the dunning for the debt.
Before the term of shemittat kesafim the creditor has rights to be repaid and can demand repayment from the debtor. After the term of shemittat kesafim has passed, the burden moves to the debtor who must now be the one who demands of himself the act, the obligation, of repayment.
Shemittat kesafim transforms the right of the creditor into the duty of the debtor. After shemittat kesafim the entire population gets to behave like the privileged, who repay out of duty rather than out of requirement.
What shemittat kesafim really means is that the debt moves from the personal to the general. It now becomes society's responsibility to have the individual debt be repaid.
We need to understand better the difference between a personal obligation and a public duty. The obligation that comes from respecting someone's rights can morph into a duty to respect those rights.
The more obligations become duties, the more autonomy reigns in the society where the ordinary citizen acts out of abundance and the privilege abundance affords rather than out of coersion and the scarcity that coerces.
A society that is free to choose but where every choice is a coersion is an enslaved society.