Instead of borrowing $10,000 to pay a medical bill and having to pay an extra $2000 in interest, under Sharia law you borrow $10,000 with a fixed-return markup of $2000.
Instead of paying interest on a mortgage (decreasing over time), under Sharia law you pay rent on the house you’ve mortgaged (decreasing over time.)
Instead of not qualifying for a loan, under Sharia law you don’t qualify for a loan.