These are not things that are bad, just things I personally dislike.
-WASD keys that are not exactly like the keys around them. A different color is ok, but I hate it when suddenly part of my keyboard feels different when typing (profile, surface texture, shape).
-Keycaps that fit loosely and wobble when you put some pressure on the sides.
-Having too many different colors and different style keycaps on one keyboard. It may be impressive if they are rare, and I can appreciate a nice collection, but aesthetically I do not like it.
-Blank keycaps. Dont get me wrong, they look fantastic, it is just that they are such a bother to use for me. Yes I touch type, and even when programming and using latex I know where most keys are. Still, it is too inconvenient for me ( I can not , for example, type something with one hand, or use numerical keys in rapid succession on a tenkeyless)
-Backlit anything. It looks cool, but under any lighting conditions except for no light at all, large clear legends are easier to read for me. It also seems a bit excessive because really, how often do you look at your keyboard when you are using it. I also do not like the constant "glow" from my keyboard as I am doing something else.
-Built in wrist rests. They are always too low to be of any practical use to me, and when they can not be removed they will actually prevent you from using a wristrest that would actually be useful.
- Rubbers/ feet that are fragile. I move and re-position my keyboard a lot , and there are plenty of keyboards that can not cope with it. In fact, even the filco rubbers on the feet get worn down in no time.
- Elaborate drivers that cause more issues than they provide useful features.