One thing I think hurt the 919 and bikes like it is the "sport" aspect. Yes, speed sells, but many of us want a true UJM. And for me, that means sitting straight up(and my feet right below, not out in front of me). The 919 puts you leaning forward more like a sport bike than a UJM. Us GHOFs with bad backs just can't do that.
As far as the "bigger is better" thing, yes a decent sized bike is nice for those long days on the highway, but how much of that do we really do? A huge majority of our daily travel is around town. To and from work, trips to the store, other errands. I used to weekend about 1.5 hours from home, and did the trip on my CB125S a few times. By choice! I have done a few poker runs on it as well. Yes, I had a little trouble keeping up, but when can you run a bike all out and not attract the attention of the police?