This didn't work. I have also checked out the updates from Epson, the support system says 'there are no drivers for this OS' so it does look like it's an issue with the Epson L355 driver and the Mojave print dialogue. It WILL print high quality from Adobe products that use a slightly different print screen. I have contacted Epson, but I don't hold much hope. This is really, really annoying!
-------
Message to Epson:
Hi, we have epson L355 printers and there is no support for Mojave on OS. It will only print in basic quality, churns the prints out fast and with lines. If you print via photoshop it will allow you to print in best quality. In Mojave it ignores the settings chosen in 'printer features'. This means you cannot print correctly from the default OS print interface. There is no update for this printer online to make it compatible with the latest Mac update (Mojave). There are already several forum posts cropping up about this. Have you got a driver update that I can access and that you can release ASAP?
EPSON L355 running all the latest updates, MacBook Pro running Mojave. The system print dialogue has changed and the L355 is no longer listening to it.
-------