Well, I don't think you're here to have your mind changed. You have already made it up. And it doesn't matter that I have more experience than you because you clearly don't care.
Anyway, I'm not saying that all the orders delivered were bad. Maybe they were all truly perfect. I can't know that. I'm saying that based on what I see, as a translator myself, there's a chance that things weren't completely perfect.
Also, their prices are very low. Buyers at that price level usually do not care much about quality. Additionally, how can a buyer check the quality of the translation unless they know the language themselves or know somebody who does? It's impossible. So, buyers like these might return, never knowing that they got subpar work. The ones who realize, though, they might leave negative private feedback.