I was making about $35K per year but was careful to have excellent credit. It can be done.
Renegotiating isn't the same as refinancing. You can see the refinance rates lower down on the page you linked above. The rates are significantly lower.
Refinancing student loan debt is an extremely common scenario. It's not an impossible edge case. It would be difficult to do if the person had worked themselves into a situation where they have unreasonably high debt burdens (e.g. $200K+) but no career to speak of, so it's not a magic bullet.
There is a way: income-driven repayment plans. There are several flavors, but you pay ~10% of (your_income - 1.5 x federal_poverty_wage). The poverty guideline depends on household size (info here: https://aspe.hhs.gov/topics/poverty-economic-mobility/povert...). Most loans are eligible.
Any balance that is left after 20 years is forgiven. It’s a lot harder to default on these loans, and it’s the best way out for people with an insurmountable amount of debt. Actually, it’s probably the best repayment plan for most people, and there has been talk about making them the default plan.
However, you may have to pay taxes in the forgiven amount. There are some edge cases where you could pay more over the life of the loan if your income increases dramatically, but it’s unlikely.
More info: https://studentaid.gov/manage-loans/repayment/plans/income-d...