It seems like this is an upstream problem, that we need come up with more substantial projects before we even get to the shaping stage.
Shape Up with the six week cycles is designed to help make progress on substantial projects. If you only have small things to do all the time, and you don’t have any trouble shipping those, then some other approach would probably work fine, like a kanban or ticket-based system.
My question would be what kind of progress you are trying to make on the product and whether you are trying to accomplish bigger changes, from the leadership level.
If you feel like bigger changes are needed but don’t know what they are, then yes Jobs To Be Done is a good flashlight to use to look around in the dark. Then with more clarity on where people are struggling you can frame meaningful projects.