Leonardo DaVinci was trying to say that sometimes the simplest things are the best way to go, for example, the iPhone had no keypad, Steve jobs kept everything simple and in the end, his product gained even more popularity than the phones with complex keypads. But it's not easy to make things simple, it is like trying to descibe a 1000 word book in a single sentence. So it makes simplicity quite sophisticated too.
He is trying to say that even a difficult problem has a simple solution.Less is more.
He means that simplicity can be applied to even the most difficult situations. Complexity does not mean it holds more information.
It is easy to pack many things into a big bag with many compartments, but one does not simply do the same with a smaller and simpler bag. To achieve that feat, one must have sophisticated thinking.
This is somewhat similar to the "Say no to 100 things" rule made by steve jobs himself
He means that sometimes, it is better to be simple than to be complicated, and the result would be even more sophisticated than the complicated mentioned earlier in my comment.
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He means that simple items that work are the best.For example according to ,urban legend, since ball-point pens could not write in space,NASA spent a lot of money to develop a pen that could write in space while the Soviet Union simply used a pencil.
He means that making something simple is always better than making something so complicated to someone but it serves the same purpose.
I think what he meant was less is more.If something simple can serve the purpose of something that is complex then the simple is more sophisticated.
To me ,what it means is that,to be innovative and improve something, is easier than to think of something brand new.
He means that a simple to function object is the better compared to a highly intricate and complex object.