I classify plain protein powder as a "food" not a "supplement". It's a convenience form of food that can be used in place of beef, eggs, fish at times and places where it is inconvenient to prepare and eat those foods. But you don't NEED protein powder to build muscle if you can eat enough real food, and you shouldn't rely on it or overdo it in any event.
Fair enough. I classify protein drinks (MRPs, weight gainers, protein powders) as supplements, because they provide super-contentrated forms of nutrients that, in some cases, are difficult to get in certain volume from regular food.
That said, protein powder makes up a relatively small part of the world we call "supplements", and 95% of what is being sold by supp companies is useless crap.
I wouldn't go as far as deeming 95% of supplements as useless. It's one of those cases of "Them that's got shall get; Them that's not shall lose". If your diet is terrible, all the NO-XPLODE, CELL-TECH, Methyl 1-D, etc. in the world won't put any sinew on your frame.
However, with your nutritional regime on point, supplements like these can help give you a boost or a kick-start to obtain that extra size and strength. The key to remember, as you may well agree, is that supplements are just that.....SUPPLEMENTS.