I would say that any image can be "changed" to manipulate it's look but it's by no means a given that improvement can be made. Improvement can only be defined when the expectations for the job are known.
For my own work it depends on how hard I worked at the shoot and how well I've defined my "normal" processes for a given film. My goal is to be completely done creatively when the shutter drops. This is especially true of weddings.
I crop with my feet and my zooms, I look for natural vignettes and frames and context, I use flash, skrims, and reflectors to burn and dodge and control contrast.
At the end of the day I'm pretty well done and the film can be processed "normally" and printed without special work in the enlarger.
There is no sin in providing great camera work and letting someone else do the rest.