Why the Sixth Amendment is important to the accused in this country, but also to the criminal justice system in its entirety?

Because establishes five principles regarding the rights of the accused in a criminal trial.

Explanation:

The sixth amendment of the United States Constitution establishes five principles regarding the rights of the accused in a criminal trial: the right to a rapid and public trial, the right to be tried by an impartial jury, the right to be informed about the charges, the right to summon witnesses and face them, and the right to a lawyer.