Reviews that people leave for products purchased are very reliable. As a consumer, I look at not only the start ratings but the comments as well. I look at the other information as well such as purchase date and where they are from. Those reviews that detail a consumers' experiences inform us of the pros and cons.
It's not a secret that many reviews on Amazon are incentivized. It's true of any review that you read online. The only reviews that you can really trust are the negative ones. Otherwise, a person probably received something for what they said. It's better to read the negative reviews for a more honest review of the product, rather than just trusting what someone else got paid to say.
No, I've found out that you definitely cannot trust the reviews on Amazon. Sellers are giving away free and cheap products in exchange for reviews. Most reviewers don't care about being honest--they just want to keep giving good reviews so the sellers will send more freebies their way. It's a terrible system.
Reviews that appear on the Amazon website are not trustworthy. There are companies that pay reviewers to write their opinion, which automatically slants the viewpoint, Even if they are not told explicitly to write a favorable review, a writer will likely do so in order to gain favor and continue to get work.
Some wit noted that when the Soviet Union fell apart freedom became much more expensive in the free world. These days even scientific research is increasingly corrupted by money doing all the driving. Amazon and every other website online simply set their standards for honesty according to whatever the market will bare which is about as low it goes when over half the US population demands the government and mass media they call evil lie to them for their own protection.