Do you think a bit of this is whiny AP holders? "Wahhh, they gave me this free thing and they dared to allow a bunch of others to do it as well." I mean, I don't think Disney said that this would be a "low crowd" event, and it's something you are not paying any extra for - Disney's choices are to either really limit the number of people that can attend or allow lots of people to attend and have longer lines. Maybe unlike the DVC events they feel the base is too large to have lighter crowds.
The one complaint I can get behind is not clearing out the regular park guests. They've gotten pretty good at this with the Halloween party and even the Moonlight Magic night they seemed to get all the regular guests out pretty quickly. Disappointing that they didn't do the same thing for this.