Just about, and I think the quicker people realize this, the better. I myself wasted a lot of time on these powders, and wish someone would have told me the 6 grams of sugar on the label was deceptive. That I was actually getting 200-300 grams (total)of high glycemic carbohydrates skyrocketing my insulin levels through out the day. I would not classify MRP's and Muscle Milk as "weight gainers", thought I don't use either, I think they generally are good products.
All they ( guys who need the extra calories) need is a little boost from food and supplement sources that primarily provide an anabolic muscle building environment, not a fat storage environment. Not saying you are going to completely avoid fat gain, but from research and experience, reduce the rate and potential of it. So I say with the exception of the link I provided earlier (and any WG product without malto) "weight gainers" should be avoided.