So, Bobtrips, would you say intentionally tilted horizons are "outside the box" now? I would say they have been tried, found lacking and tossed out. The eye wants to make the horizon level, even when their head is crooked. I think that is why a crooked horizon is easy to overlook when editing a photo. The editor must be careful and "look" for it. (I think art photographers make the horizon level or really crooked or obviously tilted, not just a bit crooked so the viewer has to decide whether intention or not.)
Blurred waterfalls are "inside the box," but you would toss them out? My guess is inside to stay. I think people see waterfalls as at least a little blurred.
Maybe photography tries to mimic real life? Seems the most often heard complaint (that at least I hear) is the image doesn't look "real." So, out of focus? Get glasses. Overexposed? Get sunglasses.
"Inside/outside what box?" was the first thing that hit me upon reading this post. Certainly they are outside the National Geographic/Arizona Highways box, as I understand the limits of that particular box. They aren't "realistic". It's not what one would have seen were they standing where the tripod stood.
(A 1/2,000 second shutter speed shot that freezes a single drop of water is also not "realistic", but closer. With concentration I can see a single drop as it falls.)
But unless we are talking about a specific box (realistic landscape, abstract fashion, whatever) I think we should be careful about discarding photographs based on either content or technique. If someone likes it, it's liked.
That said, I think at times someone introduces a novel treatment, be it crooked horizons, intentional "smearing" by long exposures, exaggerated grain, oversaturation, etc. that are entertaining, even thought provoking in their presentation. But often those treatments are adopted by many, many photographers and become trite.
Milky water has, to me, become as distasteful as those paintings of big eyed kids that were so popular a few decades back. Interesting on first or second view. Off putting by the thousandth.
One of the most "digged" images on the web (hope that is a meaningful statement) is one of a waterfall in eastern Europe. It's a very beautiful set of moderate-height waterfalls shot at a very low shutter speed. While admired by many, to me it looks as if there has been a major catastrophe at an ice cream plant upstream. Hundreds of thousands of melted vanilla are rushing downstream....
So, yes, I am talking about personal bias. But putting my bias in the context of "too much of a good thing can give one a belly ache".