Interesting question! The Constitution was, necessarily, 'incomplete.' It is only a skeleton describing a government, and such a skeleton is by necessity rather 'bare bones' if you will.

They were trying this for only the second time, the Articles of Confederation bring the first attempt, and sketching out in too much detail would have constrained the proposed government.

Conversely, there was much fear over a too powerful federal government. Many folks wanted fewer powers and laws, and a weaker system.

As regards the Bill of Rights, they did not want to list certain rights so that others, not listed, would also be protected. An enumerated list of rights tends to give governments the idea that "if the right is not listed, it does not exist."

The bill of rights was adopted as a concession to the States and Commonwealth's to secure their adoption of the new constitution.

I'm a bit sick, so apologies for any incoherence