I too prefer to use and will do, my little village PO , until told this is not possible, and I do not use Simple Delivery until again, it becomes mandatory.
When creating a new listing here's how to opt out:
Click on Custom Postage option, this is next to the simple delivery option on the listing on the right hand side, and it should allow you to then select your postage options.
The above is when using a PC / laptop sorry I don't use the app but imagine it must be in a similar place.
You may need a laptop / PC and use Chrome, perhaps the app or mobile device is limited for the above action.
@nellyboylesemporium