Many times we feel reluctant to disparage other people's work. Usually, they are doing the best they can. However, often they could be doing much better than that. And ultimately, the world needs us all to do great work. We shouldn't kill the cheaters, but we might want to let them go out of business.
The problem is that we tend to blame the supplier of the service. Sure, they might be holding back, like the light bulb cartel did, in the early years of the last century. On the other hand, many companies are doing their best.... only their best is not quite good enough, and sometimes not quite good full stop.
That situation sadly prevails at the great majority of companies which do GMAT prep. And if there were one single reason for this, it would have to be that you, dear client, are that fabled goose that lays golden eggs: the One-Time Buyer.
You have never before signed-up for a GMAT course, and you are unlikely to ever enroll in another. You have hardly no basis for comparison, and no reason to think you need one. You take the course. It might even be fun. But I am sad to say you are not in position to evaluate the product. It just isn't an easy call, like a film review would be.
Not many people will take one course and understand in time that a 600 and 700 score are fully 32 percentile ranks apart. A 600 is all that's required to enter the Premaster program at Erasmus, but for a top 10 MBA candidate, 600 is basically a failing grade. These two demographics cannot sit in the same class without wasting each other's time. But in nearly every single GMAT course, they do.
Furthermore, how are you to know the meaning of taking a Computer Adaptive Test? This is still a new kind of test, and not many of us have ever heard of it, let alone trained for it. So it is possible, if the school wants, to fobb you off with an English teacher, as if this was a test of American Literature. Most of the English teachers who double as GMAT Verbal experts have not yet taken the test, and hence could be forgiven for not knowing the difference between Grammar on tv and Grammar at the race track. And some of the schools might be forgiven too, especially if they've been in the business only three or four years. But many of them do know the difference, and just don't want to pay for expertise. Reason: they know that you are a one-time buyer.