This is way too reductive. In the US, credit cards are complicated. For instance, I get about 2.5% of every purchase back, either in cash or kind. Yes, the merchant pays 4%, and VISA/matercard take a bit, and my issuing bank takes a bit, but calling that "extracting rents" feels like pure rhetoric.
FedNow is awesome and will make the market more efficient, but merchants aren't going to lower prices due to lower fees, especially while there's a mix of fee-less transactions and credit card transactions. At least in the short term, adopting FedNow is just giving money to the places you buy from (for retail transactions).