Shouldn't the reviewer know the product, be able to place this speaker in the proper context? Describe the sound, what you are getting for the money? How it was designed to be used? If not, he is a bad reviewer. It would be like a guy taking a lawnmower and using it as hedge clippers and then reviewing it saying is a terrible hedge clipper and it cut off my hands to boot.
Up to a point yes. And, in fairness, most reviewers who have been doing this for a while are entirely able to contextualise in the vast majority of cases.
But this only works up to a point. You still have to do some matching of person to product. A reviewer should be flexible enough not to let their own tastes dictate the tone of the review too strongly, but there are physical, domestic, and price concerns to take into account. Many reviewers have a self-imposed upper and lower limit in terms of loudspeaker size and even system cost, in part because things significantly beyond those limits are outside their area of specialism. For example, I can confidently say the DALI Zensor 1 is the best budget loudspeaker I've heard, but I've not heard enough current budget speakers to say they are the best budget loudspeakers with confidence because that market sector is presently outside my remit.
It's the editor's role to make sure the reviewer is sufficiently grounded in a given sector of the market to comment upon that product as fairly as possible.
It's not really a question of using a lawnmower as hedge clippers. It's about not giving the biggest ride-on petrol driven mower you've ever seen to the guy who only reviews hover mowers on his postage stamp sized lawn and expecting good results.