I wouldn't say it was that, necessarily. A bunch of us devs are hobbyists, meanwhile there's a significant chance a bunch of the artists taking part in Famicase are industry professionals, and as such likely have inboxes stuffed to bursting at the best of times; a request from a complete stranger can easily get overlooked in that sort of situation.
The thing I'm taking away from this is to remember that Famicase and AGBIC are annual things, so I ought to be ready and get more messages out sooner next time 👍
(Also Google Translate is your friend - I've been able to get permissions from two Japanese artists thanks to it 😊)