Actually, the Nicene Creed does say you “must believe.” It says unless you believe it you cannot be saved, but will perish everlatingly.
Maybe we are reading a different Nicene Creed.
This is the one at Holy Mass on Sunday from my memory.
I believe in God the Father almighty
Creator of Heaven and Earth
I believe in Jesus Christ His only son
Our Lord
Who was conceived of the Holy Spirit
Born of the Virgin Mary
Suffered under Pontius Pilot
Was Crucified, died and was buried
He decended into Hell
On the third day He arose again from the dead
He asended into Heaven
And is seated at the right hand of God
The Father almighty
He shall come again to judge the living and the dead
I believe in the Holy Spirit
The Holy Catholic Church
The communion of saints
The forgiveness of sins
The resurection of the body
And life ever lasting
Amen
Nicene Creed
We believe in one God,
the Father, the Almighty,
maker of heaven and earth
of all that is, seen and unseen.
We believe in one Lord, Jesus Christ,
the only Son of God,
eternally begotten of the Father,
God from God,
light from light
true God from true God,
begotten, not made,
of one Being with the Father,
through him all things were made.
For us men and for our salvation,
he came down from heaven:
by the power of the Holy Spirit
he became incarnate from the Virgin Mary,
and was made man.
For our sake he was crucified under Pontius Pilate;
He suffered death and was buried.
On the third day he rose again
in accordance with the scriptures;
he ascended into Heaven
and is seated at the right hand of the Father:
He will come again in glory to judge the living and the dead,
and his kingdom will have no end.
We believe in the Holy Spirit, the Lord, the giver of life,
who proceeds from the Father [and the Son.]*
With the Father and the Son he is worshipped and glorified.
He has spoken through the prophets.
We believe in one holy catholic and apostolic church.
We acknowledge one baptism for the forgiveness of sins,
We look for the resurrection of the dead,
and the life of the world to come.
Amen.