I think that's a bit like saying "when I have a successful painting career, then I can judge others' art". You can competently evaluate things without being an expert at building them. Probably my favorite rating system is the one used for Deadly Rooms of Death over at the Caravel forums, which separates into a 10-point "fun" scale and a, completely separate, 10-point "difficulty" scale. From a creator's standpoint, nothing beats actual, verbal feedback, but for someone looking for something to play, having at least some concept of the average numerical opinion of others is definitely much better than the vague information that x people pressed a button whose precise meaning is itself too vague to be helpful (is it "I didn't completely hate this", "I really, really enjoyed this", or something in between?).
I don't feel terribly strongly about this, but it does seem weird after three straight games (CW 1-3; I played particle fleet but don't remember participating in its custom maps myself) of having (to me) a very sensible, 10-point rating system, to go to something much less useful in almost every way I can think of.