I've never understood the appeal of using a product like Affirm, especially if you already have a credit card. Credit cards already give you a 30-day grace period before purchases start accruing interest. Using Affirm to extend that to 42 days seems inconsequential. It seems like their target customer are people bad with credit, which would make them predatory.
Also for bigger purchases, it's better than a credit card. I pay my Amex balance off every month, but during the pandemic I used Affirm to purchase a home gym setup, and paid it over the course of 6 months at a much lower interest rate.
They are definitely not predatory in my view, but I don't have the perspective of a low-income person anymore.