Scripture says God created mankind “in his own image…in the image of God he created them”. (Genesis 1:27)
Therefore, it’s reasonable that God the Father, the first person of the Trinity, be depicted (for example in art) as a man.
Scripture also says that Jesus Christ was the Son of God. Jesus was born of a human mother, had a human body on earth, grew from a human baby to an adult human man, experienced human death on the cross, and the Church teaches that Jesus had both a human nature and a divine nature.
Jesus is God and is the second person of the Trinity.
Therefore, it’s reasonable that God the Son (Jesus) be depicted as a man.
God the Holy Spirit, the third person of the Trinity, is a spirit and has been described (I think by Bishop Barron) as being the love between the Father and the Son. God the Holy Spirit is not generally depicted as a man. Sometimes the Holy Spirit is shown as a dove, sometimes as a ray of light, sometimes as a rushing wind (as described in Scripture) etc.
It’s important to remember that the three persons of the Trinity are not constrained by the depictions of them in art. Each person of God could appear in any form they wanted. God could appear as light. But it is not wrong to paint him looking like a man, as he could also appear as a man.
