Indeed, I have heard about the exploit of the game engine, where one would fill his substitute slots with as low star players as he could find, such that he would be placed in a Cup bracket full of lower level teams, and perhaps also face lower quality teams in the Champions League and the regular season. Some people would say that "This is the way it is, get on with it." But I'm saying that it doesn't have to be this way, and it's easily changeable by Nordeus, as shown in how the bracket creation rules have changed twice this year already.
From the game developer's point of view, it doesn't make sense to make the game no fun for its players. And this type of hopeless disadvantage is not worth spending loads of real money on anyways.