The lack of a single codified curriculum makes it difficult to take one bad version of CGS and condemn the entire program. However, this lack of transparency is, of itself, an object to be criticized.
During the reign of Pius X, the bishops throughout the world were ordered to create catechisms based on the pope's own catechism, containing all the doctrines required to be taught to children. In America, this became known as the Baltimore Catechism. Though other catechism systems of different a style may be used, they must cover the same content.
CGS fails to cover many of essential Catholic doctrines contained in the official catechism of the US bishops. The outline for what is to be taught is not based on Catholicism, but on the personal preferences of the founders of CGS. Though there are good elements used in the program, such as a 3D diagram of the city of Jerusalem, at best time is wasted on frivolous endeavors instead of teaching the fundamentals of the Catholic faith. If students of CGS cannot answer basic questions about the Catholic Faith, it is because the founders themselves decided the children did not need to learn this information.
"According to Cavalletti, she and Gobbi made many mistakes and had to throw away some of the materials they had created as they searched to find the essential themes and elements that correspond to the needs of the children. Only materials that aroused much interest and deep joy were kept. They were seeking the most essential and the simplest materials that would help the personal work of the children so that the children would be able to grasp the message of the Scripture or the liturgy. Therefore, anything that was not essential was removed from the atrium." https://www.biola.edu/talbot/ce20/database/sofia-cavalletti
This has caused the Level One Atrium to jettison many of the important particular Catholic teachings such as angles, sanctifying grace, the Trinity, and Marian doctrines. Though the Level One Atrium may mention some of these fundamental concepts in a Bible passage, they are not taught in-depth. Part of the reason for simplicity and a lack of structure is that the founders of CGS believed that the Catechist is not to teach.
"She works from the theological assumption that Catechesis offers children the opportunity to relate to God whom "they innately know and perceive." It is not a "catechesis of definition but a catechesis of invitation. invitation""https://www.biola.edu/talbot/ce20/database/sofia-cavalletti
The CGS system reduces the role of the catechist to a mere presenter, but not a teacher. They are not there to convey the faith, but to facilitate the class. Below are just two of the 32 Points of Reflection of the CGS. These reveal the failure of CGS to pass on the Faith.
3. The atrium is a community in which children and adults live together a religious experience which facilitates participation in the wider community of the family, the church and other social spheres. The atrium is a place in which the only Teacher is Christ; both children and adults place themselves in a listening stance before his Word and seek to penetrate the mystery of the liturgical celebration. 4. The transmission of the Christian message in the atrium has a celebrative character. The catechist is not a teacher, remembering that the only Teacher is Christ himself. The catechist renounces every form of control (such as quizzes, texts, exams, etc.) in the spirit of poverty before an experience whose fruits are not her/his own. https://www.cgsusa.org/discover/the-cgs-method-past/the-32-points-of-reflection/
If no one is passing down the Faith, then the children will be ignorant of the Church's teachings. The method by which the Faith is expected to be passed down is derived from Maria Montessori's idea of 'vital immanence'. This is a concept that is found in eastern spirituality, but condemned as an error by the Roman Magisterium.