Simply stated, Isaiah 28 isn't a recommendation for a teaching method, it's the description of how certain people were infantile in their understanding.
Much love!
So you didn't read the rest... of that Isaiah 28 chapter? like verses 23-29?
It is... about a specific Bible study method, the one that God Himself reveals. When reading the Isaiah 28:13 verse, it is pointing out how understanding in The Word of God is, "... precept upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little...;". And for that reason, those who refuse to do it that way fall backward, become snared, and taken in deception.
That point was actually covered earlier in Isaiah 8, which involved a history of the "kingdom of Israel" (northern ten tribe kingdom at Samaria), and how they relied more on the king of Assyria instead of God, so God brought the Assyrians upon them, and is giving them warning. But He also included a warning of the Assyrian coming through Judah also, which points more towards the very end of this world just prior to Christ's future coming, since the king of Assyria never conquered Judah-Jerusalem, but will try to in the last days.
The only... way to understand that is to stay line upon line with the flow of the chapter...
Isa 8:4-17
4 For before the child shall have knowledge to cry, "My father, and my mother", the riches of Damascus and the spoil of Samaria shall be taken away before the king of Assyria.
The subject of the coming Assyrian is continued from the Isaiah 7 chapter. Isaiah is told by God the child's name Maher-shalal-hash-baz means 'he hastenth to take the spoil, he speed to seize the prey'. The child was to be a sign of the coming Assyria to destroy.
5 The LORD spake also unto me again, saying,
6 'Forasmuch as this people refuseth the waters of Shiloah that go softly, and rejoice in Rezin and Remaliah's son;
7 Now therefore, behold, the Lord bringeth up upon them the waters of the river, strong and many, even the king of Assyria, and all his glory: and he shall come up over all his channels, and go over all his banks:
8 And he shall pass through Judah; he shall overflow and go over, he shall reach even to the neck; and the stretching out of his wings shall fill the breadth of thy land, O Immanuel.
That is a subject turn from the destruction of Samaria, the northern ten tribe kingdom that the king of Assyria would take per 2 Kings 17 and remove all the ten tribes captive to Assyria, and instead to the Assyrian coming upon Judea-Jerusalem, which is for the latter days. God uses that waters as a flood metaphor even about the dragon-serpent of Revelation 12 that is cast down to the earth for the time of future great tribulation, and goes after the symbolic woman that keep God's commandments and have the Testimony of Jesus Christ.
9 Associate yourselves, O ye people, and ye shall be broken in pieces; and give ear, all ye of far countries: gird yourselves, and ye shall be broken in pieces; gird yourselves, and ye shall be broken in pieces.
10 Take counsel together, and it shall come to nought; speak the word, and it shall not stand: for God is with us.
That is actually what the joining of nations of today is about, today's movement towards a "one world government", which is to be the Revelation 13 beast kingdom of ten horns, seven heads, and ten crowns, lasting 42 months with power over all... nations. God is saying, "Go ahead, join yourselves. I'm going to bring it all down!"
11 For the LORD spake thus to me with a strong hand, and instructed me that I should not walk in the way of this people, saying,
12 "Say ye not, 'A confederacy', to all them to whom this people shall say, 'A confederacy'; neither fear ye their fear, nor be afraid.
13 Sanctify the LORD of hosts Himself; and let Him be your fear, and let Him be your dread.
God told Isaiah to not proclaim what those deceived do, with saying, "A confederacy", with that joining of nations. Instead, let Him be our fear, fear Him instead, which points to our need to RESPECT what God has said, and put our TRUST IN HIM instead. Apostle Paul showed in the last days just prior to Christ's future return, the deceived will be saying, "Peace and safety", revealing this confederacy of nations is what the deceived put their trust in, and not in God.
14 And He shall be for a sanctuary; but for a stone of stumbling and for a rock of offence to both the houses of Israel, for a gin and for a snare to the inhabitants of Jerusalem.
15 And many among them shall stumble, and fall, and be broken, and be snared, and be taken.
And there it is, God and His Word shall be "... a stone of stumbling and for a rock of offence to both houses of Israel, for a gin and for a snare to the inhabitants of Jerusalem. And many among them shall STUMBLE, AND FALL, AND BE BROKEN, AND BE SNARED, AND BE TAKEN. Why is that? Because they do not STAY in His Word line upon line. They instead teach and follow their 'own' word.
16 Bind up the testimony, seal the law among My disciples.
17 And I will wait upon the LORD, That hideth His face from the house of Jacob, and I will look for Him.
KJV
Christ's true disciples know to wait upon The LORD to come, even though for the latter days He hides His face from the house of Jacob (both houses of Israel), which will occur during the coming "great tribulation" by the symbolic "Assyrian."
God's faithful saints under His Son Jesus Christ that do STAY in His Word line upon line, are His DISCIPLES. That word disciple involves the word discipline. Jesus said if you STAY in His Word you will be His disciples indeed, and The Truth will make you free. That is about getting understanding... in His Word by that line upon line discipline. Apostle Paul in 2 Timothy 2:15 even called that idea as becoming a "workman" in The Word, showing oneself approved of God by doing it that way.