You got it, the catechism is not dogma per se. It’s a simplified, lay-oriented reference to teachings and doctrine. It also is not Canon Law.
Dogma is truth. Dogma cannot change because it’s revealed by God. For example, the Immaculate Conception and the Resurrection are both dogmas of the faith. The Church does not have many; I believe there are about 200 of them.
Only one of those is supported by and found in Scripture....the Resurrection.
The Immaculate Conception is not found in nor supported by Scripture.