Is it permissible to work in interest-based banks, especially since some scholarly fatwas forbid that, based on the verse: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression"? And does this verse apply to everyone who works in a non-Islamic institution or one that is hostile to Muslims?

Muslims are required to strive to reform their reality to conform to Sharia (definition), not to demand that Sharia conforms to a corrupt reality. Those who work in usurious banks include those directly involved in usury, such as accountants and managers, and those who assist them, such as those who sell to them or lease to them. The sin of the direct perpetrator differs from the sin of the collaborator, even though they share in the sin. The requirement is to reform reality to conform to Sharia, not for Sharia to adapt to a flawed reality. Necessities have their rulings, and working in a usurious bank may be permissible out of a compelling necessity. A layperson follows whoever they trust in their knowledge and piety when scholars differ.