The U.S. site for this device shows only Catalina 10.15 support. The drivers and supporting software were released in Oct. 2019 — essentially the first release timeframe of Catalina 10.15.0, so you should have looked before you upgraded to Big Sur, as this device is not among those supported by Apple's AirPrint in Big Sur, and without software support from Epson, you have a paper-weight.
If you performed a Time Machine backup of your prior operating system before upgrading to Big Sur, you can potentially revert to the older operating system, your data, and D700 support — by booting into Recovery mode (⌘+R), and choosing Restore from Time Machine Backup, which will wipe the startup drive, and repave with the backup contents.