When Jesus warns us "In your prayers, do not rattle on like the pagans", he is not condemning long prayers as such but only those that are marked by a sheer multiplication of words.

The long prayers that we do serve a real purpose in the development and teaching of our faith. Thus, the Creed we recite at Mass is indeed a long prayer and even a rather complicated one. It is so because it is a necessary summary of our faith and is the product, not of a sheer multiplication of words but as the fruit of long reflection and discussion in the early Church.

It is about the correct way to understand how to speak about Jesus and his true relations with God the Father and God the Holy Spirit.

The Creed offers us a profound and succinct expression of our Christological and Trinitarian doctrine and as such, is to be cherished and appreciated. Then having taught us about our proper attitude in prayer, Jesus goes on to teach us the perfect prayer. Which, in spite of its brevity teaches us much about the contents and consequences of our faith and our Spiritual lives.