There's probably too many rejections to give any feedback. I mean if there were 10,000 to 20,000 groups that applied it would be impossible to send a reason in the email to each group. Besides it all comes down to a numerical rating (sauce for the goose). Kudos to the bird with a golden egg.
I think two years ago, the last they posted their numbers, there were 421 applications. This year, I'm just guessing, but likely somewhere between 2 to 4 times that.
They are no longer posting their numbers, so don't ask.