First of all, leaning on wisdom of man, is that what you do when you lean on the wisdom of the apostles and those that were taught directly from the apostles? Ignatius and Polycarp were disciples of John. Clement of Rome was a disciple of Peter. I think we are to listen to the men of the early Church for obvious reasons.
You can not rely on that your understanding of scripture is totally from the Holy Spirit. If the Holy Spirit shows you something in the scripture and you know it's the Holy Spirit speaking, you are blessed. This is not something that happens on ordinary basis.
You tell me why we have all these different churches and denominations, if the Holy Spirit clearly lays out the Bible for us on daily basis?
Leaning on the wisdom that is put in the Scriptures by the apostles and prophets is relying on God.
Relying on people, even those taught by God, is relying on people.
Ignatius and Polycarp were men, and anything they say must be verified with Scripture.
Even the Bereans did not just accept Paul's words (At that point his words weren't verified Scripture) they searched the Scriptures to make sure that what Paul was telling them was the truth.
Whenever something is given secondhand, errors can creep in.
In my business I make keys for others. I use original keys to make copies, I never copy a copy. Because the copy, no matter how close to the original, is not an original.
So with the truths of God.
Whenever I hear a truth, I check it with the Scripture. And if Scripture disagrees, I deny what I was told.
God used the Apostles and prophets to write the Scriptures for us. This is as close as we can get to God speaking to us Himself.
As for why we have so many denominations, people either don't listen to what the Holy Spirit is telling them through His Word or they misinterpret what He has told them.
As for this idea that God rarely speaks to us today.
What happened to the Voice of Jesus that we are supposed to know?