This doctrine is laid out on this blog. I won't attempt to restate it, because if I do people will come out of the woodwork stating that I have misrepresented what that person (who desires to remain anonymous) teaches.
Does God's word come from your imagination, or from God?
Jesus said that everything he taught came from the Father: "...as my Father hath taught me, I speak these things." ( John 8:28). If Jesus, the Son of God, was limited in the worth he could provide by what he was given from the Father, who among us can think for a second that what we produce can be good? Jesus said,
4 Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.
5 I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing.
(John 15)
We are told plainly that our thoughts are different from God's:
8 For my thoughts are not your thoughts, neither are your ways my ways, saith the Lord.
9 For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts.
(Isaiah 55)
Real experiences with God rarely confirm what we were already thinking. Instead, they almost always cause radical paradigm shifts from our thoughts to help us align with God's thoughts. They eviscerate our sacred cows and preconceived notions.
How can you, for a second, think that you can acquire God's word through exercising your imagination? To do so would require thinking that you can somehow organically produce what only God himself can provide.
Proponents of this doctrine describe one's imagination as training wheels to help along the process of accessing God. Some use hallucinogens to "kick start" this process, describing how it is necessary to train yourself to come to the point where you can receive revelation in the standard way as described in the scriptures: From God to you. It is very odd that anyone would believe this, given that it is noticeably absent from and apparently contradicted by scripture. In response to this argument, one person told me that "the scriptures don't really teach you how to connect to God." This is exceedingly preposterous. First, connecting to God is the purpose of the gospel. If you had a calculus textbook that did not actually teach calculus, but only taught bits about addition, subtraction, and multiplication, it would be quite useless. Second, that this process is taught very plainly in the scriptures is evidenced by the contents of my book on the topic "Seek Ye This Jesus," which contains hundreds of scriptures that do exactly that.
God does not come from our conjuring him.
Now, proponents of this doctrine will say that they are not conjuring Jesus, but are giving him space to appear, etc. When you follow a list of steps and expect Jesus to appear in that moment, that is the definition of conjuring. God does not appear at the summons of man. Jesus said "I proceeded forth and came from God; neither came I of myself, but he sent me." (John 8:42) If Jesus himself doesn't even dictate when and how he appears, how on earth can you think that your imagination can?
Connection with heaven comes as a result of the will of God, not your imagination or desires. What you pray and how you are as a person can affect the will of God, but the idea that somehow you can dictate what experiences God gives you is not supported at all in the scriptures, and is actually contrary to what we see there.
Sometimes God or angels respond directly to prayers. However, prayer is more often the process of getting to that point than the terminal activity. Adam prayed for a very long time before an angel appeared to him. Daniel prayed for weeks before Gabriel came. These are not rare examples. If men as righteous as Adam and Daniel could not conjure God in instances much more important than your life, what makes you think that you can?
Do imaginary experiences with God cause you to repent?
The point of the gospel is to provide you with a pathway to attain God's character in your own. Those who know God have overcome sin in their lives.
6 ...whosoever sinneth hath not seen him, neither known him.
7 Little children, let no man deceive you: he that doeth righteousness is righteous, even as he is righteous.
8 He that committeth sin is of the devil...
9 Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God.
(1 John 3)
There is a tendency to redefine what it means to repent, to reconcile yourself to God. It means to live in a way that you are living up to all truth that God has revealed to you, constantly and without exception. Those who have not attained this state are not yet at the point where Jesus' sacrifice atones for their sins. They cannot endure his glory. They cannot dwell with him.
It is highly suspect when people tell me that they have been promised eternal life and yet continue in willful sin. I have yet to meet any proponent of this doctrine that can tell me that they have repented of all their sins. God's real interactions with men cause them to change for the better. Meanwhile, his ability to reveal himself to you is bounded by how much you have come to be like him.
Satan and men can generate experiences that exalt the person without having paid the price of repentance. This is Satan's interest because it robs the individual of sufficient desire to actually repent, and freezes their spiritual progression before they actually reach the end of the road.
Imaginary promises are vain.
Overcoming the world requires the sacrifice of all things. Do imaginary promises provide you the faith, hope, and security you require to sacrifice all things?
If your imaginary promises have not brought you to repent of all of your sins, the answer is no, since they could not even bring you to sacrifice what little you currently know you need to sacrifice, let alone all the things you will be asked to do/change in the future.
Not all spiritual experiences are from God.
Because there is opposition in all things, we should expect that any experience we have could be from Satan. We have to test it. What is the test?
11 But he that believeth these things which I have spoken, him will I visit with the manifestations of my Spirit, and he shall know and bear record. For because of my Spirit he shall know that these things are true; for it persuadeth men to do good.
12 And whatsoever thing persuadeth men to do good is of me; for good cometh of none save it be of me. I am the same that leadeth men to all good; he that will not believe my words will not believe me—that I am; and he that will not believe me will not believe the Father who sent me. For behold, I am the Father, I am the light, and the life, and the truth of the world. (Ether 4)
If it leads you to repent--to adhere to what God has taught you in every way in all places and at all times--it is good. If your experiences merely flatter you, they are not from God. God does not exalt sinners. He humbles them. He shows them that they need to change. When you are abased and actually repent, he will exalt you with blessings and promises. That is the pattern laid out in scripture.
...Put your trust in that Spirit which leadeth to do good—yea, to do justly, to walk humbly, to judge righteously; and this is my Spirit. (D&C 11:12)
Experiences can come from men, God, or Satan. Those that come from God are of worth. Those generated by men or Satan are not.
So much more available.
Even if these imagination experiences are real, so what? Why stop there? Why settle for the crumbs that fall off the table? If you are really a son or daughter of God, keep repenting and strive for the greater experiences, the ones described in the scriptures. Do not assume that just because you have been invited to the banquet, you are assigned to the seats of honor. Keep striving and repenting until you literally stand in the real presence of God, and receive promises from him in ways that cannot be doubted.