I do sometimes think there are other words that might be more appropriate for the context: parsimony or consistency are related concepts that could be more precise.
But there are some things that are just simple, like a Bankers Box.
we could try defining a new word for specifically this sense of 'simple'. for example, 'fivous', 'blorsy', 'bonatchy', 'jatomurous', or 'wislous'. the problem is that if the word gets adopted, it's likely to undergo the same sense shifts as its synonym 'simple'
But there are some things that are just simple, like a Bankers Box.