First of all, let me say I agree with everything Astrid and Gryffin have said. To me, there are degrees of negative language we use if we are expressing a subjective opinion--some terms sting more than others because of their connotations, while others can be mitigated because they can be elaborated on using more precise, concrete language so it becomes clearer why the observer is making that judgement.
And, Angie, you are SO right words like "frumpy", "dowdy", and "dumpy" are a real pet peeve. I think my reaction is based on the limp "Well, I can't explain it, but I just know it when I see it" explanation that usually comes when the person pronouncing the judgement is pressed for a followup. Really, the speaker can just say a plain "ugh" and leave it at that for all the help those words give a person. Now, if someone wants to use those terms to describe their own appearance, that's entirely different, much like I can say I feel fat in a dress, but woe betide Mr. Gaylene if he told me I looked fat in that dress.
One of the best aspects of YLF is the careful, but concrete, evaluations that people give when asked to comment on an outfit. Telling someone an outfit looks dated because of the size of the shoulder pads can be helpful; telling someone an outfit is clownish, or dull, or unfashionable, or frumpy says zilch except that the observer didn't like it.
Carla, while it's true that most times "frumpy" is used by the wearer not the observer, that's not always the case. It was all I could do to not write a sarcastic response to one commenter a few months back who posted "Ooohhh, frumpy!!! Looks like something my mother would wear!" Well, hello, honey, I'm old enough to be your grandmother, so I'm guessing said outfit would be too young for me to even consider...