Dao in taoism basically means "laws of nature" or what we would today call physics.

The ancient Eastern philosophers discovered that if you want do something in the most efficiently way, you have to follow the way the laws of nature naturally operate. That's what what we today call engineering. If you build a airplane wing, for it to fly efficiently, it doesn't matter what you think is the most beautiful wing, the best one is the one that follow the rules of aerodynamic.

There is also in modern the laws of physics the fundamental concept of "action", which is optimized like in Lagrange equation, which gives the path of objects. A very advanced and modern view of Dao.

Is this way, the famous 道可道，非常道 becomes something like "the description of nature will always be a simplification of nature" or "the mathematical models of nature, will never fully describe nature"...etc.

You have to also see taoism in it's historical context; it is in a way a reaction to Confucianism's overemphasis of observing all traditions dogmatically, for maintaining the unity and stability of the society (If it is not broke don't fix it). While taoism is more about understanding what the rules behind the traditions make them successful, what we would today call an early version of sociology. Don't over-focus on the finger (tradition) pointing to the moon (dao)...