Well, that has an easy explanation. Most people want Nintendo to do better with third parties, yes, but they don't want it instead of first party. And right now, even if it's not really true, there's a bit of a perception that Nintendo 1st party news has dried up since there hasn't been much new since February (I don't mean updates on XC3 or Pokemon, but new announcements and such, like Prime 1 and Fire Emblem).
(most) Nintendo fans are always going to be 1st-party focused. If this had been a General Direct announcement, or if they had done something like a 1st party showcase and then had a long 3rd-party Direct not long after, then everyone would be on board, I think. It's mostly just the timing.