This beats my ears. I think this 'plates in the kitchen' actually means, that there are too many (unserved) dishes there.
Platos can be either plates or dishes. So, it would depend on the context.
I just made a simple typo, where I wrote: "There are to many plates in the kitchen," and Duolingo declined it. Kind of uptight, DL.
DL is teaching all of us to spell better, but the reason why your translation was declined is because the words "too" and "to" are different parts of speech. "Too" is an adjective, and "to" is a preposition. Although simple mispellings like "yse" for "yes" are often flagged by DL, most computer programs, except perhaps Watson, are not yet smart enough to extrapolate the differences between homonyms.