If the wait staff aren't kind and the food isn't appealing, just leave

Don't dine and dash; that's not what I'm advocating. Rather, don't let sunk cost fallacy force you into wasting time and money you'd rather spend elsewhere. What's the point of paying to be miserable? Moreover, what's keeping you there, and what do you hope to achieve by sticking it out? Imaginary social custom that you need to stay until dessert? A signed prenup agreement with the host?

If it helps, think of it as the restaurant failing to live up to the minimum standard of a pleasant meal out, not an inherent inadequacy on your part. There are so many good restaurants in the world, and if this isn't one of them for you, don't force it. Politely explain that nothing on the menu has caught your eye, pay for the drinks, if any, and go elsewhere. It won't be worse.

Nothing, nothing, says you have to suffer through aggressive condescension and $24 flaccid eggs on toast because you walked through the door. It swings two ways for a reason.