No amount of processing can add detail that isn't there to begin with. If you greatly overexpose your picture, you cannot rescue the highlight detail lost. The same with significantly underexposing your picture. Additionally, attempting to fix some perspective problems will make the picture look unnatural and sometimes even cartoonish.

Getting it right in the camera is still a matter of pragmatism. It's a question of whether you want to spend several hours in front of a computer retouching the picture, or spend a couple of minutes getting your camera settings right.

Some things might be better done in post processing because you have more control, such as multiple exposures. However, this class of post processing has more to do with special effects rather than proper exposure.

I'm also of the opinion that you should never use "I'll fix it in post" to do a mediocre job taking your picture the first time. An extra minute or two at the time of exposure is well worth saving hours in front of a computer. As my college professor once said, "No matter how much you polish a turd, it's still a turd."