Explanation:

Article 50 of the constitution says, “The state shall take steps to separate the judiciary from the executive in the public services of the state.” In most of the states of India, the separation of judiciary from the executive has taken place.
It is part of Directive Principles of State Policy (DPSP) not Preamble.

Preamble of constitution of India-
WE, THE PEOPLE OF INDIA, having solemnly resolved to constitute India into a [SOVEREIGN SOCIALIST SECULAR DEMOCRATIC REPUBLIC] and to secure to all its citizens:

JUSTICE, social, economic and political;

LIBERTY of thought, expression, belief, faith and worship;

EQUALITY of status and of opportunity;

and to promote among them all

FRATERNITY assuring the dignity of the individual and the [unity and integrity of the Nation];

IN OUR CONSTITUENT ASSEMBLY this twenty-sixth day of November, 1949, do HEREBY ADOPT, ENACT AND GIVE TO OURSELVES THIS CONSTITUTION.