Please stop using “simplistic” when you want to say something is simple but are trying to sound like you’re smart, because what you’re actually doing is making yourself look stupid.
Simplistic is pejorative; when you describe something as simplistic, you’re criticizing it as being oversimplified to a fault. It does not mean something is well-designed, clean, uncluttered, easy to use, efficient or in any way positive.
An example of the wrong use of “simplistic” is clear in this review of a waffle maker by Consumer Reports:
So, the translation of CR’s bottom line is that this waffle maker is “a highly affordable, poorly designed and superficial model with great results.” Obviously this is not the intended meaning, because it even goes on to describe it as a “quality waffle maker.”
It is the writer and the copyeditor that are not quality here.
If you’re want to be positive, the word you’re looking for is just good ole “simple.” Use it, and quit trying to sound clever.