Be wise as serpents, harmless as doves.
I agree gullibility is not a great trait, discernment is truly the key to spiritual freedom.
HOWEVER, it is harder for a rich man to enter the kingdom of heaven than it is for a camel to enter the eye of the needle. Consider, "rich" means "rich" in beliefs. The more with "Think" we "know", the more likely we are to cut ourselves off from Divine revelation, from Truth, which is truly Infinite.
As soon as we create an image of what "God is" and who is saved and who is not, and we "know the answers" of creation, well, we've shut ourselves off from Truth, because human minds cannot even begin to understand the mysteries of creation which are infinite and always transcending themselves.
We must "Be as a child to enter the kingdom of heaven that is inside of us, at hand, Now".
Meaning: Curious, always asking questions, no attachments, KNOWING we KNOW NOTHING!
There is always MORE.
Attachments to beliefs are exactly what keep us out of the kingdom of heaven. Reality is much more than our thoughts or beliefs and we will experience suffering should we choose to identify with our thoughts and beliefs, which by their nature, are limited and false. There is always a higher Truth.
As soon as we're 'teachers' and no longer students, then I would suggest we are students who are failing Schoolroom Earth
~ Because there is always MORE, and each of us, yes each of us, has pieces of the puzzle.
Love your neighbor as yourSelf
Shine your Light and Be, but judge not, for we will be judged by the standards we use to judge others (I would suggest this is cosmic law*)