This is an issue concerning the authority of the Church. We Catholics believe that Jesus established his Church under the Chief Shepherd, Peter. Again, Jesus himself is the Good Shepherd, but Peter shares in Jesus’ Shepherd-ship. Jesus, the Davidiac King, establishes in Peter a Prime Ministerial role. Again, the type for Peter can be found for this in Eli’akim:
Isiah 22:16-22
"Thus says the Lord GOD of hosts, “Come, go to this steward, to Shebna, who is over the household, and say to him: 16 What have you to do here and whom have you here, that you have hewn here a tomb for yourself, you who hew a tomb on the height, and carve a habitation for yourself in the rock? 17 Behold, the LORD will hurl you away violently, O you strong man. He will seize firm hold on you, 18 and whirl you round and round, and throw you like a ball into a wide land; there you shall die, and there shall be your splendid chariots, you shame of your master’s house. 19 I will thrust you from your office, and you will be cast down from your station. 20 In that day I will call my servant Eli’akim the son of Hilki’ah, 21 and I will clothe him with your robe, and will bind your girdle on him, and will commit your authority to his hand; and he shall be a father to the inhabitants of Jerusalem and to the house of Judah. 22 And I will place on his shoulder the key of the house of David; he shall open, and none shall shut; and he shall shut, and none shall open.”
Here, two things are clear. The Key of the house of David signifies both the authority given to him within the Kingdom, and also the succession of office. With this, he is given the authority to bind and loose - rabbinic term signifying the authority to forbid and permit; to give the final word. In the same way, the Kingdom of Heaven has its Heavenly King, Jesus, who bestows his authority on his Earthly representative, Peter and his successors, who have been given the authority to give the final word.
This is only possible because of the Holy Spirit’s guidance. So, as you see, I am not denying Holy Spirit’s capability (that is a presumption on your part), but I am saying that the authority rests upon Peter’s successors and those in communion with him. It only makes sense. Through this unity, Christians - for 1500 years - affirmed, for example, the Real Presence in the Eucharist. Now, there are well over 1000 (that is the most conservative estimate I could make) denominations, who disagree on such a fundamental doctrine. They all claim to be led by the Holy Spirit. It seems clear to me that the Holy Spirit can not guide them in that particular way