Ohh I've had this conversation so many times...
Hate is a strong word but, I'm definitely not a fan. To clarify, I don't think they're running out of ideas, because in all honesty I really think they upped the ante in creativity with the Gen V designs. But there's a few reasons I don't like these two evolutionary lines.
For one, they are pretty poorly designed IMO. This has nothing to do with what they are (garbage and ice cream), but the design. To put it bluntly, they don't look like Pokemon. As a demonstration of what I mean, imagine this: imagine you had seen them before you had any knowledge of Gen V, and no context. Would you even guess that they were Pokemon? My first thought when I see them is "ice cream cone/garbage heap with a face", not "ice cream Pokemon/garbage heap Pokemon". Compare that to Zoroark. Immediately recognizable as a Pokemon.
Another thing is the concepts. Garbage and ice cream just aren't very interesting things to anthropomorphize. Of course, they're not the only offenders in this regard (looking at you, Mr. Gen I floating rock with arms).
And of course, there's their evolution. Trubbish goes from garbage to more garbage, and Vanillite goes from ice cream cone, to bigger ice cream cone, to bigger ice cream cone with two scoops. Blegh...they I know they could have thought of something better. Again they're not the only offenders, but I think it made a bit more sense with Magneton, because when a Magnemite gets strong enough its magnet pulls in other Magnemites.
I think the biggest one is the first one--they just don't look like Pokemon. But they can't be all perfect. For having designed over 718 of them, I think they've done a darn good job making most of them creative and interesting :)