I think it is more complicated than that. I think folks will look at cost and then compare that cost with a restaurant at home and more often than not, it is less expensive at home. The food may be comparable, but the cost is not, so there can be buyers remorse. With regards to "the best" I firmly believe that nostalgia plays a huge part in those responses.
I also think that personal taste enters into the conversation. There are restaurants that I simply don't like. I don't care if the theme in awesome (I am talking about you Coral Reef) the meals just are not great, and when you factor the cost in, the time commitment for that dining experience, I know I am going to choose to dine elsewhere.
I do think that one of the factors is expectation. I expect the meals I pay for in WDW to be decent. I look at reviews, prices and selection. I do not expect 5 star dining, and I do expect that I will pay more for everything than I would at home. For signature experiences, I know I am going to pay a premium, and if I book those restaurants, I know what my budget will be before I even enter. So far, I have never been disappointed. I will say that for us, even though we dine out often at home, we still enjoy dining in WDW. A lot. My husband and I are carried away with nostalgia so the memories impact our enjoyment, and my adult children and grandchildren are very much dining down memory lane as well. I think what happened to the OP is that the cost is very much factoring into the satisfaction.