The Magisterium and the Church Fathers

The magisterium has explicitly ruled that an old earth position is an acceptable theological opinion among catholics. According to the personal opinion of many in the magisterium, they seem to think it is the more probable one. So i will fully hold that no catholic should be saying some one is a heretic for saying they hold to an old earth. And if you came to believe that that were the case, would you perhaps struggle to believe in god in some way?