An average hides the shape of the distribution

One number cannot describe hundreds of different experiences, and it does not try to.

Two items can carry the same overall rating and be entirely different propositions. One earns it because nearly everybody found it good and unremarkable. The other earns it because half the buyers were delighted and half had something go badly wrong, and the two halves cancel out into a respectable middle. The first is a safe purchase. The second is a gamble with a pleasant-looking average. Nothing about the headline figure distinguishes them, which is why the distribution matters more than the mean. The average is a summary of people, not of the product, and summarising a divided group produces a figure that describes nobody in it.

So look at the spread before you look at the score. A rating that clusters tightly suggests a consistent product and a reasonably accurate description, because people are broadly getting what they expected. A rating split into two peaks suggests either variable quality between individual units, or a description that suits one kind of buyer and misleads another. Neither is disqualifying. Both change what you should check next, and a split usually tells you exactly which question to answer before deciding. Very often that question is simply which of the two camps you belong to, and the reviews themselves will tell you if you read a few from each side.

Volume matters too, but not in the way it is usually treated. A large number of ratings makes the average more stable, not more relevant, and stability is only useful if the underlying group resembles you. A hundred ratings from people using something in a way you never will is less informative than a dozen from people whose situation matches yours. Read for resemblance before you read for quantity, and the scores will start to mean something specific rather than general. A handful of reviews written by people with your constraints is worth more than a wall of enthusiasm from people whose constraints you do not share.