Let me try to explain with a bit of an overstatement: Most TV is crap, but year after year they keep making it. People making it cannot be good at it? Well actually they are. They found the sweet-spot by maximizing the profit in terms of eyeball captured they will make from the least amount of effort. That is success.
Now-a-day successful politicians are far better at making people vote for them than actually realizing the platform they are elected on. They are literally good at the game of democracy, but don't know what to do with the spoils. The difference between those two seems to be "fake-news".
Lets assume that the prolific reviewer on Amazon is completely legit. He is obviously good in the sense of efficient at reading and writing reviews. That we do not see the "good" in an outcome of having so many reviews written by the same person does not make his activity less good as an activity.