It is not possible that by deciding the basics only, the Constitution would be ready too and there would be no point in having a Constituent Assembly. The basics were related to the universal adult franchise, right to freedom and equality and protection of the rights of minorities in the constitution of independent India.

These basics were the guiding principles to set the Constitution for the welfare of society. That's why the Constituent Assembly was made in India, even if all the basics of the Constitution were already decided.