There was neither Dao nor Daoists before Laozi and Zhuangzi.

Only if you believe that Dao is the universal principle you are a Daoist. If you can't name "Dao" as "Dao" you aren't a Daoist. That's easy - by definition.

That the "constant/eternal Dao can't be named" is trivial. The constant/eternal table can't be named too. The constant/eternal chair too. That's nothing special for "Dao". The name is not the object/thing/phenomenon. I wonder about your fascination for that" the name is not the thing" ....

Lao and Zhuang actually *did* invent the Dao. Before Laozi and Zhuangzi no Dao as "the universal principle". The Dao before Laozi and Zhuangzi was a "way" for man and society in chinese philosophy. The Confucianists and the Legalists and the Mohists had their "Dao" - but it wasn't "the Dao" , the Great Dao (Da Dao).

We don't know if there is a "great Dao" as the Daoists believe.

My question is:

As it seems you are believing in Dao - what is your explanation of your Dao? Seems to be a very specific one.