I have to agree with you that we cannot fully depend on the Holy Spirit.
The Holy Spirit makes us understand truth, but we have to be told what that truth is when it's not
very clear.
I hope I am miss understanding what you mean by we can not fully depend on the Holy Spirit. I depend on the Holy Spirit 100% to teach me all truths as when I study I pray and ask the Holy Spirit to guide me through the scriptures opening my eyes to all truths. He will take me through the revelations of the OT cross referencing with the revelations of the NT as I study word by word, verse by verses chapter by chapter and the history of the various eras. Do I always understand what the Spirit of Good is teaching, not always as the Holy Spirit will work through others with a greater Spiritual knowledge then I have.
Now Satan will throw a few people in the mix trying to teach his twisted word, but we need to learn how to Spiritually discern what spirit is teaching us as the wolf (Satan) will always come in sheep clothing trying to deceive the mind of many, 1 John 4:1-6.
John 14:23 Jesus answered and said unto him, If a man love me, he will keep my words: and my Father will love him, and we will come unto him, and make our abode with him.
John 14:24 He that loveth me not keepeth not my sayings: and the word which ye hear is not mine, but the Father's which sent me.
John 14:25 These things have I spoken unto you, being yet present with you.
John 14:26 But the Comforter, which is the Holy Ghost, whom the Father will send in my name,
he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.
1John 2:27 But the anointing which ye have received of him abideth in you, and
ye need not that any man teach you: but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as it hath taught you, ye shall abide in him.