The Law of Attraction draws three distinct objections, and they are worth keeping apart because they carry different weight.
The first is empirical. The claim that directed thought influences external events is a causal claim, it has been available for testing for well over a century, and it has not been supported. Where it appears to work, ordinary explanations are sufficient: a person who forms a specific intention attends differently, acts differently, asks for things they would not otherwise have asked for, and notices openings they would have walked past. Promoters frequently accept exactly this account and present it as vindication. It is a different claim, and it does not need the metaphysics.
The second is methodological, and it is the sharper one. The doctrine is built so that failure cannot register against it. If the desired thing arrives, the law worked. If it does not, belief was insufficient, or a contrary thought was harboured, or the universe had something better in view. No outcome is treated as disconfirming, which is what people mean when they call it unfalsifiable, and it is also what makes the teaching so durable in the face of experience.
The third is moral, and it has drawn the most sustained comment. If circumstances follow from thought, then circumstances are evidence about thought. That conclusion follows directly, and promoters have not consistently avoided drawing it: that the sick attracted their illness, that the poor attracted their poverty, that people caught in disasters or atrocities were at some level in accord with what happened to them. Critics have pressed this point hard, and the answers from within the movement have ranged from careful qualification to statements that make the implication entirely explicit. The objection is not that promoters intend cruelty; most plainly do not. It is that the logic of the doctrine delivers it anyway, and that the burden this places on people who are already suffering is real and falls on them regardless of what was intended.
There is a fourth consideration which is not an objection to the idea but to a particular use of it. Mental attitude is sold as an alternative to medical treatment for serious illness, and as an alternative to organised action against material conditions. Where that substitution is made, the cost is borne by the person who made it.