I've rarely seen rubbish images that can be "saved" by photoshop.
you can make it look ludicrous and garish, or perhaps briefly interesting to the untrained eye, but rarely can they be made into something great. unless the person is really a talented photoshopper, in which case, that is an art form unto itself. it's actually quite similar to collage art (that forgotten art form), which can actually be deeply immersive if done correctly.
If you are talking about a bad exposed vs perfect exposed image, I 100% agree. There is a dramatic different to the trained eye when viewing an image with perfect exposure vs one that is a stop underexpose or overexposed. I will die with my light meter in my hand )
Is there really such a thing as a 'perfectly' exposed image? There's only so many stops in a dynamic range, and once that's exceeded you either clip the highlights or squash the shadows. Some might choose to blow the highlights because they want the shadows where others might want the sky, others might bracket for HDR in which case Exposure hardly matters at all other than on the monitor screen histogram.
Certain scenes just don't expose properly anyway fog mist or soft lighting always appears under exposed, in other conditions light meters get fooled snow - also often for cut outs.
Very little in photography needs to be 'perfect' and those who get hung up on technical perfection often seem to forget the main purpose - that is creating images. Technically imperfect interesting images which draw the viewer in or make contact or say something, appeal to me far more than a bland but perfect snapshot.