Why was John the Baptist not excited at seeing Jesus at Jordan?

St. Thomas Aquinas refers to Lk. 1:41 when commentating on Jn. 1:29:

Note that after the conception of Christ, when his mother, the Virgin, went in haste to the mountainous country to visit John’s mother, Elizabeth, that John, still in his mother’s womb and unable to speak, leaped in her womb as though performing a religious dance out of reverence for Christ. And as then, so even now; for when Christ comes to John out of humility, John offers his testimony and reverence and breaks out saying, Look! There is the Lamb of God.

Origen does, too (as quoted in St. Thomas's Catena Aurea on Jn. 1):

After this testimony, Jesus is seen coming to John, not only persevering in his confession, but also advanced in goodness: as is intimated by the second day. Wherefore it is said, The next day John sees Jesus coming to him. Long before this, the Mother of Jesus, as soon as she had conceived Him, went to see the mother of John then pregnant; and as soon as the sound of Mary’s salutation reached the ears of Elisabeth, John leaped in the womb: but now the Baptist himself after his testimony sees Jesus coming. Men are first prepared by hearing from others, and then see with their own eyes. The example of Mary going to see Elisabeth her interior, and the Son of God going to see the Baptist, should teach us modesty and fervent charity to our inferiors. What place the Savior came from when He came to the Baptist we are not told here; but we find it in Matthew, Then comes Jesus from Galilee to Jordan unto John to be baptized of him.

Why was John the Baptist not excited at seeing Jesus at Jordan?

Doubt the Catholic Church has a stance on this issue. Besides that, just because Scriptures do not state that John the Baptist did not seem excited at seeing Jesus at the Jordan, it does not mean that he was not excited at seeing Jesus at the Jordan. John the Baptist could very easily suppressed his feeling when Jesus came to be baptized. He was the Precursor after all and he was fulfilling his role as a Prophet.

We are given the story of the ministry of John the Baptist, called the Precursor or Forerunner of the Lord, with some variation of detail, in the three synoptic Gospels of Matthew, Mark, and Luke, as well as in the Book of John. Luke tells us of the birth of John the Baptist in a town of Judaea, about six months before the birth of the Saviour. The attendant circumstances, which we have already recounted under the headings of "St. Elizabeth" and "St. Zachary", his parents, suggest the miraculous and wonderful. The New Testament tells us nothing of John's early years, but we know that his pious, virtuous parents must have reared the boy with care, conscious always of the important work to which he was appointed, and imbuing him with a sense of his destiny.

When John began final preparations for his mission, he was probably in his thirty-second year. He withdrew into the harsh, rocky desert beyond the Jordan to fast and pray, as was the ancient custom of holy men. We are told that he kept himself alive by eating locusts and wild honey and wore a rough garment of camel's hair, tied with a leathern girdle. When he came back to start preaching in the villages of Judaea, he was haggard and uncouth, but his eyes burned with zeal and his voice carried deep conviction...Although his preaching and baptizing continued for some months during the Saviour's own ministry, John always made plain that he was merely the Forerunner.

The Scriptures tell us of the day when Jesus joined the group of those who wished to receive baptism at John's hands. John knew Jesus for the Messiah they had so long expected, and at first excused himself as unworthy. Then, in obedience to Jesus, he acquiesced and baptized Him. Although sinless, Jesus chose to be baptized in order to identify Himself with the human lot. And when He arose from the waters of the Jordan, where the rite was performed, "the heavens opened and the Spirit as a dove descended. And there came a voice from the heavens, Thou art my beloved Son, in Thee I am well pleased" (Mark 1, 11). - Saint John the Baptist the Precursor

John the Baptist sticks to his mission. The Baptist points the way to the Christ: "He must increase, but I must decrease" ([John 3:30).

We must remember that the public ministry of Jesus has not yet begin and that it was St. John the Baptist who was to prepare the way of the Lord. "He is the one who comes after me, the straps of whose sandals I am not worthy to untie." (John 1:27)

After Jesus was baptized by John the Baptist as described in Mark 1:9–11, He then immediately spent 40 days in the wilderness where He was tempted by Satan. After that, He returned to the area where John was baptizing. John 1:29 states that Jesus returned and the day after John the Baptist had been questioned by the Jews. John the Baptist identified Jesus as the Messiah using such language, as we would expect for a prophet, referring back to ideas written by past prophets.

I am sure that John the Baptist saw these things and rejoiced, at least interiorly. Jesus mentions to us that Abraham saw His day and rejoiced, yet the Old Testament is absent of that fact. "Your father Abraham rejoiced at the thought of seeing my day; he saw it and was glad"(John 8:56). The same may be true about the Forerunner of the Lord.