It's important to remember that there are so many factors that can influence people's reviews.
Example, Ohanas has always been one of my favorite restaurants. I have never had a bad experience there. Well, aside from when I took a group of teenagers, and after eating plates full of peanut sauce soaked noodles, one of them announces he was allergic to peanuts. But, not Disney's fault, and Disney handled it amazingly well. Anywho.....
Second to last time I went with my sister, she was seated on the side of the table that was right on the coconut races route. She came away saying that she didn't understand why she ever liked Ohanas, and it was just a horrible experience.
When we went last week, I requested a table away from the coconut races route. The entire party, my sister included, said it was one of the best meals of the trip. Her fiance joked about going on a trip where they ate at Ohanas every night, because it was that good. So she looked up pricing to stay at the Polynesian, because she was on board!
Now, both of these experiences, to me, were similar as far as food and service. But apparently, being knocked one too many times by a broomstick trying to hit a coconut was just enough to ruin the whole experience on the previous trip!
I'm not saying that servers might not have off nights, or that sometimes a chef might overcook or underseason something. But that is true of any restaurant. So people may experience an off night, they may be affected by the atmosphere or environment, but that means it can also be a wonderful dining experience - which is why it's still my favorite!