The complaints you're seeing are almost always about the same thing, someone went with a supplier offering prices that seemed too good to be true and got burned. Chasing the lowest possible cost from whoever you find first is where it goes wrong. Read through whether dropshipping is actually a scam here:
https://easync.io/articles/dropshipping-a-scam/ . It breaks down what separates the legitimate side of it from the stuff that gives the whole thing a bad reputation.