Make everything as simple as possible, but not simpler.An aphorism attributed to Albert Einstein.
But how could you determine if the UI you designed could (and should) be made optimally simpler — meaning can still be made more simple than the current without losing anything of value to the users (and while adding more value as well)?
First, market data
Given that the product is in the market already, gather insights on the usage of the product and the UI’s role in it.
Are there complaints pertaining to a particular screen / page? Look deeper into those.
Create a UI prototype of a solution — but remember, your solution is only a hypothesis or an assumption. You could uncover the efficiency of this revised UI in terms of its usability by conducting a usability testing with users.
Optimize the UI based on the results and insights gathered from the usability testing.
Put the optimized UI in the market because that’s the only way you could really gather useful insights if your proposed solution works better than it was before.
Notice that I’ve focused on optimization rather than simplicity.
In simplicity — you might fall into the trap of only making the interface and interaction more simple than before and think you’re done.
In optimization — you must be aware about many factors (including simplicity) playing well with each other in achieving a common goal.
As Einstein said, “…but not simpler.” That’s optimization, right there.