Hi,
You mentioned that the printer drivers had been updated. Were these the 5.12.1(2403) drivers released 03/21/2023 (XeroxDrivers_5.12.1_2403.dmg)?
Was everything (including scanning) working as it should before the change from Wi-Fi to USB?
The Xerox WorkCentre 6515 Color Multifunction Printer is listed in About AirPrint - Apple Support as a model supporting the AirPrint technology. An AirPrint model can be used without having to install additional drivers, provided that the printer and the Mac are connected to the same network. AirPrint works with wireless (Wi-Fi) or wired (Ethernet) network connections.
Have you checked whether there is a change with the printer wired by Ethernet to one of the LAN ports of a Wi-Fi router instead of using the broken wireless connection (and instead of using USB, which would require drivers anyway)? The iMac should still be able to connect wirelessly (via the router).
If necessary, if you wish to connect the printer wirelessly, it should be possible to use a wireless Ethernet bridge, or a standard Wi-Fi range extender with Ethernet bridge capabilities, connected to the Ethernet port of the printer.