An inherently well designed product can get a bad review for several reasons. First is that it may have been damaged in shipment but not visibly, so the reviewer gets a product that is not working properly for no obvious reason. Second is that an inherently good product by design can be operated improperly and so does not perform as it should, possibly because the reviewer can't follow instructions.
Suppose there's a product that's competently designed but poorly assembled. Four out of five reviews are favorable, but the remaining reviews complain about cold solder joints, poor cabinet paint jobs, parts rattling around in the case, etc. My question is, does a product so poorly assembled that one out of five are unacceptable out of the box constitute an inherently good product? I might argue that it's well designed, but I don't think you can call it inherently good if the assembly process is that poor. I'd say this is a case of a product that isn't inherently good but gets legitimately good reviews.
An inherently bad product (a product that by design cannot work well or properly) cannot get an unbiased good review by fair reviewers. There is not normally any misreading of instructions or mis-adjusting of settings that can make a flawed electronics design work properly. It could get a good review, but only because of a person wanting to bias the numbers for personal or company gain.
Take a look at the reviews for the Eico 753, arguably one of the worst transceivers ever sold. Yet you'll find seemingly sincere five-star reviews. Why? Because some people thought (a) it was cheap, and it met the expectations that the low price established, (b) fixing it to work halfway well was a valuable learning experience, or (c) it was better than what they'd owned previously. True, one or two of these reviews might be from people who have a tenuous relationship with reality, but most of the five-star reviews seem to be from folks who are genuinely thoughtful. Like it or not, the criteria for what constitutes a good product will vary from person to person.
So what I'm saying is that in the case of a product with many good reviews, and only a few very bad ones, it is wise to throw out the bad reviews.
I'd also say that in the case of a product with many good reviews, I'd throw out the few bad ones, but only after reading them to see if they mention an objection that might be relevant to me.
The bottom line is, the written portions of the reviews speak louder than the numeric ratings.