A lot of wire transfer code and other foundational banking code is written in COBOL.

Not thanks to Java or OOP, but despite it. You can thank my colleagues fighting Java in the bank each day.

And that needs skyscrapers and entire financial districts to achieve? This is a tiny fraction of the "work" done by the financial sector. Most of what they do is pointless trading between themselves and sapping the output of the real economy.

The banks' real "product" is trust. You will work an entire month for a "bank transfer" (something you can't even hold, let alone eat or burn) because you believe your landlord will similarly accept a "bank transfer" in exchange for you rent (or, if you have a mortgage, you work an entire month because you believe this means you will be able to continue living in your house unchallenged). This has absolutely nothing to do with what programming languages or paradigms they have in place.

With so many issues and costs that people buy stablecoins to exchange money with smart-contracts that have no substantial guarantee other than the issuer's right to block funds...