Why would I read it from the Amplified, when that translation has DELIBERATELY PERVERTED what is written?
We will focus on just two verses (Isa 28:9,10 KJV) since that is what we are talking about as applicable to Christians. There is also a great deal of rebuke for Israel, but that's a different topic.
Whom shall He teach knowledge? and whom shall He make to understand doctrine? them that are weaned from the milk, and drawn from the breasts. For precept must be upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little:
1. Who is the Divine Teacher of Christians? The Holy Spirit (hence the capitalization)
2. Whom does the Spirit make to understand doctrine (the meat of the Word)? Mature Christians (not babes in Christ) -- those who have been weaned from the *milk* of the Word of God (the elementary truths of the Gospel).
The apostle Paul has the same instruction for Christians in Hebrew 5:11-14, and he ties it in with knowing how to discern between good and evil (and act on it, which goes without saying, since actions speak louder than words)
HEBREWS 5 (KJV)
11 Of whom we have many things to say, and hard to be uttered, seeing ye are dull of hearing.
12 For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk, and not of strong meat.
13 For every one that useth milk is unskilful in the word of righteousness: for he is a babe.
14 But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.
As the OP says "A lot of things are scattered throughout the Bible... We need a good command of the entire book." And this is where Isa 28:10 comes in: For precept must be upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little: Which simply means that the Holy Spirit does not overwhelm the Christian who seeks the truth, but teaches him or her progressively.
You also made a couple of irrelevant (or inappropriate) remarks: "The body of Christ is not under law." There is not even hint about this in the OP. Therefore I called it a "knee-jerk" reaction. And strictly speaking the Body of Christ is under the Law of Christ. Which is even more demanding than the Law of Moses.
Then you said this: That’s actually a negative scripture for its saying do this, do that, and I will do this or that. And how can it possibly be negative for a Christian to do what God and Christ command, and not do what they forbid, and also expect the corresponding responses from God?