The two most important things are data and UI, the one thing we developers spend all of our time thinking and talking about is code :)
Because data >>> UI >> code.
> Also, business logic is encapsulated in code - if that's borked, no amount of UI will save it.
The assumption here is that the bare minimums are fulfilled. If the software doesn't work at all you have none of the above.
The two most important things are data and UI, the one thing we developers spend all of our time thinking and talking about is code :)