The LoA is a modern version of the Protestant Reformation, and just like religion, can keep us from living the life our higher-self intended to live.
I am a pretty whoo-hoo, new-agey sorta guy, happy to gobble up the latest fringe ideas right off the bat, and only later discard or edit such ideas. I adopt a kind of "Acceptable until proven unacceptable" policy.
So, when I first heard about the Law of Attraction is seemed good enough to consider as a real possibility. And I suppose I still feel that way, to some degree, but what I have seen more than not is that the LoA has become (or maybe always was) a form of Protestantism 2.0.
The tenants of the Protestant Reformation  were such that each person was allowed to understand and interpret the "word of god" (i.e., the Bible, for Christians) for themselves. This was a radical departure from the Catholic practice of locking the bible away and only listening to the interpretations of the church. This practice goes way past the 16th century, as my Roman Catholic Italian grandmother, born in the late 1800's, was herself scolded by her church for even owning a bible.
Martin Luther's greatest crime against the church was printing copies of the Bible in Geman (from Latin) so any individual could read it for themselves. As a result, today there are 44,000 different sects of Christianity, each with their own interpretation.
Out of Protestantism grew the extremely radical idea, and one that threatened the existence of the Catholic Church, of what came to be called the "Protestant Work Ethic," which essentially claims that one need not wait until one dies to receive their divine reward (or punishment), but rather one can be rewarded (or punished) in this life based on their good (or bad) deeds. Hence, hard, god-fearing work resulted in material wealth and health, and slothful sinners suffered their fate as well.
This is where the LoA sounds a bit derivative by stating that, rather than one having an individual relationship with God, one has an individual relationship with reality. They share the same idea that one's personal condition in life is a reflection, or measure, of the success of that relationship. Keep in mind, in the 16th century, reality and God were much more intertwined than they are today.
In both cases there is a "quid pro quo" relationship with God or reality, exchanging faith for the fulfillment of one's desires. This is evidenced by anyone who ever asked themselves "What did I do to deserve this?" or "Am I being punished for something wrong I did?" or for the already faithful "Is my faith weak?".
The foundation of LoA is that we attract into our lives that which we desire by aligning our awareness with a focus that is harmonious with that desire, and by the unshakable belief that reality is a reflection of our own nature, a very common belief among modern seekers in the West.
We can edit the original five tenants of the Protestant Reformation to apply to modern new-age culture pretty easily:
"By Scripture alone" becomes "great Universal Law that 'like attracts like'"
"By faith alone" becomes "You are one with the One Universal Mind from which all things become manifest"
"By grace alone" becomes "The creative power of your thoughts is limitless"
"By Christ alone" becomes "Through creative visualization"
An example of LoA in practice might be, focusing through creative visualization (4) on one's inner wealth (1) through gratitude (5) or sharing, will bring(2) wealth into one's life thanks to the endless bounty (3) of the universe, of which you are one with.
I am not being critical of the LoA. I am just suggesting that the LoA is something like a Protestantism 2.0. But, I also believe it overlooks or ignores something very important.
If you believe, as I do, that we have come into this life not as new creations but as old souls that have existed long before this life, and will exist long after this life, then it raises the question as to why one incarnated in the first place.
Each of us has our own path to walk, and each of us is at a different place on that path. Some of us have chosen to experience individuality, or its opposite, surrender; or power, or its opposite, enslavement. Perhaps we walk this part of our path to better know ourselves by exploring some aspect of life, or maybe we are simply plodding though some territory that is part-and-parcel to the journey of the soul. All that is known is each of us is walking our own path. Ask anyone, sinners and saints, what the purpose of life is and you get a different answer.
The purpose of life is not to be happy. It is to be useful, to be honorable, to be compassionate, to have it make some difference that you have lived and lived well.” ― Ralph Waldo Emerson
The purpose of life is to live it, to taste experience to the utmost, to reach out eagerly and without fear for newer and richer experience.” ― Eleanor Roosevelt
“The mystery of human existence lies not in just staying alive, but in finding something to live for.” ― Fyodor Dostoyevsky, The Brothers Karamazov
“The purpose of life is to contribute in some way to making things better.” ― Robert F. Kennedy
“You were ordered to obey Allah, and you were created to perform good deeds.” ― Hazrat Ali Ibn Abu-Talib A.S
“It is the amount of positive vibration you have radiated in life that matters,” ― Amit Ray, Meditation: Insights and Inspirations
“Life is the great indulgence - death the great abstinence! Therefore make the most of the HERE AND NOW! ― Anton LaVey
"The purpose of life is to realize desire is the root cause of all evil and discover the eightfold path to live life and overcome suffering" ― Something Buddha probably said
"(The purpose of life is to) seek first the Kingdom (of heaven), and all these things will be added to you.” ― Jesus
"And I did not create the jinn and humankind except to worship Me" ― Allah [Quran 51:56-58]
This dharma, or path, or theme, of one's life, is not known to the un-self-realized being. A soul caught up in the illusion of life, in ego, in materialism, does not have the ability to see the souls path. How then, is the un-self-realized able to know what the soul needs or wants? The needs and wants of someone absorbed in the mundane reality will be in direct conflict with the purpose of their path, which has been completely forgotten.
For example, one might be living a life specifically lacking in material wealth, a path chosen by the higher-self to understand humility or resourcefulness or faith, or a life of wealth to experience the fleeting value of materialism.
One also has to ask themselves why so many souls are born into a life of seeming misery, and how the LoA might work in places like Cameroon or Burkina Faso.
To the materialist, everything is measured by materialism, so it is no wonder why we are taught to measure our value in wealth and possessions.
To the vitalist (i.e. someone who believes in a 'vital spark', a 'soul', an 'élan vital') everything is measured by vitalism, and even though we inherently know this, we continue to be seduced by materialism and brainwashed by culture.
How then, can one trust their desires when they are so susceptible to seduction, programming, and brainwashing? Likewise, how can one doubt their desires if they are fully self-realized? And if one is self-realized, then there is no need to 'practice' the LoA because they are already in perfect harmony with their true selves.
Thus, the LoA is especially attractive to those that are blind to their true nature, and inevitably will use it to improve their lot in life, typically to improve their health, love life, status, wealth, power, etc. In these cases, the LoA becomes dangerous ploy because if you are not self-realized then manifesting your desires is not in your best long-term interest, and if you are self-realized, you are already living and practicing the LoA by default.