The important point is that there are 2 lists:
1. Words that can be entered as valid guesses
2. Words that are ever used as solutions in Wordle
I think this is a great design choice (and IIRC was part of the original game). That is, Wordle doesn't want to use really obscure or uncommon slang words as the solution, as that would make the game less enjoyable (I wouldn't like it so much if the solution was a word I'd never heard of). But, when I get stuck and can't think of a word that will fit as my next guess, sometimes I just go into "mash keyboard mode" so hopefully I'll find something that will fit and get more information about the solution. More often than not something fits, and I'm usually surprised my guess is an actual word.
So, to your point, DUCKY is a valid guess but will never be an actual solution in Wordle.