"Because, even because they have seduced my people, saying, Peace; and there was no peace; and one built up a wall, and, lo, others daubed it with untempered morter:"
The Hebrew used here for wall is only used x1 in the OT, and actually means a thin wall/a wall of slight or poor build.
Also, when we look to the Untempered mortar, the Hebrew means something crude, undigested, insipid.
When we put the thin poorly built wall together with the crude, undigested mortar we begin to see the state of this wall.
Why was the wall in such a state with this crude covering to make it look okay?
Because the people had been seduced, or led astray, or misled by false teachers (prophets).
Verses 11-14 show what will happen to this wall. This reminds us of the teaching of the Lord Jesus and reminds us that what we build on is of critical importance and will one day be shown for what it is:
The wise man who built his house upon the rock, which withstood the storm, unlike the foolish mans house whose foundations were upon sand. (Matt 7:24-27)
Let us not be insipid or led astray, but be building strong walls on the right foundations."LOVE THE LORD YOUR GOD WITH ..."
How depressed Ezekiel must have been! The LORD caused him to be aware of the totally godless attitude that existed in Jerusalem. He writes, “certain of the elders of Israel came to see me.” [14 v.1] The “word of the LORD” comes to him, “… these men have taken their idols into their hearts and set the stumbling block of their iniquity before their faces. Should I indeed let myself be consulted by them?” [v.3]
The lesson is plain, it is folly to come to seek God and yet retain fleshly thoughts in our minds. Ezekiel is further told, “any one of the house of Israel … who separates himself from me, taking his idols into his heart … and yet comes to a prophet to consult me through him, I, the LORD will answer him myself. And I will set my face against that man (or woman)…” [v.7,8] Surely the same applies today to those who “consult” God through reading his word – but have a wrong motive in their hearts. Peter’s words come to mind about Paul’s writings,, “There are some things in them that are hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other Scriptures.” [2 Peter 3 v.16]
In our chapter  in Luke there is some comparison with the attitude of the lawyer who asked Jesus, "Teacher, what shall I do to inherit eternal life?" He said to him, "What is written in the Law? How do you read it?" And he answered, "You shall love the Lord your God with all your heart and with all your soul and with all your strength and with all your mind, and your neighbour as yourself." [v.25-27]Jesus says to him, “You have answered correctly: do this and you will live.” But he asks, “and, who is my neighbour?” In response Jesus tells him the well-known account of the ‘Good Samaritan’ and asks the man, “Which of these three, do you think, proved to be a neighbour to the man who fell among robbers?” [v.36] He answers, “The one who showed mercy” and is told, “You go and do likewise.”
Let us all love our Lord, with all our heart, our soul, our strength and our mind showing our love by our actions day after day: of course, we will sense at times, something similar to what the LORD caused Ezekiel to sense. But surely, in at least some cases, it will cause others to “do likewise” and – for at least one or two to take serious notice of the message and meaning of what we talk about – the wonder and real meaning of the word of God – as the only ‘light’ in the darkness that covers the world today.