Jesus in the Gospel of Saint Matthew gives us an important teaching against the sins of pride and vanity, that is, the opposite of the virtues of humility and simplicity:"But many who are first will be last, and many who are last will be first", Matthew 19:30.
Recall that the Kingdom of God; that is to say dominion, empire, the government of divine perfections, implies an attitude of service towards the others: "do to others what you would have them do to you", Matthew 7:12. In other words, the "other", "the neighbor" matters, you cannot be simple and humble when our neighbor is reduced to a manipulable object. The exercise of empathy, putting ourselves in the place of the other, is essential.
This is why Jesus calls us not to look for the headboards of the tables, lest that the owner of the house force you to change your place in the table because a more important person arrived. The acception of people is a consequence of human selfishness, and is considered a serious sin (error).
In the Bible there is a description of God's love:"Love is patient, love is kind. It does not envy, it does not boast, it is not proud.It does not dishonor others, it is not self-seeking, it is not easily angered, it keeps no records of wrongs.Love does not delight in evil but rejoices with the truth. It always protects,always trusts, always hopes,always perseveres.", 1 Corinthians 13:4-7.
Humility and simplicity are virtues that are the result of a discernment, that is, a way of choosing, a mentality with this characteristics: benevolent, edifyng, progressive.
Being humble and simple does not mean not realizing what the world is, lowering your head to any outrage, but, not believing in the lies we like and feed us the ego, not believing in "beautiful lies." Being simple and humble avoids us being an easy target for flatterers, that is, for those who know how to give fallacious speeches by appealing to human selfishness.
Jesus reminds us that in the commandment of love and in the description of Charity all Christian virtues are summarized:"A new command I give you: Love one another. As I have loved you, so you must love one another. By this everyone will know that you are my disciples, If you love one another" John 13:34-35.