Let's look at Isaiah 28 more to see what ought to be avoided.
Isaiah 28:9 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.
10 For precept must be upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little:
11 For with stammering lips and another tongue will he speak to this people.
12 To whom he said, This is the rest wherewith ye may cause the weary to rest; and this is the refreshing: yet they would not hear.
13 But the word of the Lord was unto them precept upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little; that they might go, and fall backward, and be broken, and snared, and taken.
We can easily stumble if we go line by line, here a little and there a little. . . while rejecting how the weary can find rest. The Word of God is not meant to be taken here a little and there a little by studying lines of words in the Bible. We must "hear." Therein lies the struggle. If we are in the stage of depending on holy books and holy men, we are not yet weaned from the milk. We must struggle along, moving forward so that we come to hear the Voice of God for ourselves. We must also take care to look at our deeds daily to see if our fruits are good or bad. If we are bearing good fruit, we can be confident we're on the right path.
False teachers, by the way, often claim to hear the Voice of God. It is easy to follow the wrong teachers. If they are true teachers, they will get their students to the point where they no longer need them as teachers. The students grow up spiritually and can hear for themselves. This is what Jesus did with his disciples. They couldn't hear the Voice of God at first. It took a while under Jesus' discipline before they could hear for themselves.
The proper teacher does not want an eternal relationship with his students where he remains the only person considered to have authority. The proper teacher knows he can hear the Voice of God for himself -- and he wants his students to learn how to hear for themselves as well -- and he insists they advance. Thus there are stages to it -- first the milk, then the meat.
1 Corinthians 3:2 I have fed you with milk, and not with meat: for hitherto ye were not able to bear it, neither yet now are ye able.
Hebrews 5:12 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.
1 Peter 2:1 Wherefore laying aside all malice, and all guile, and hypocrisies, and envies, and all evil speakings,
2 As newborn babes, desire the sincere milk of the word, that ye may grow thereby:
Notice how heavily the disciples leaned on Jesus. That was the correct thing for them to do for the time they did it. Then the time came that they needed to grow up, and Jesus knew it. They needed to start hearing the Voice of God for themselves.
John 16:7 Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.