Totally agree about the new stuff chipping, my kitchen trim looks terrible after just two years.

Sometimes the cheap stuff just gets the job done.

Honestly, use whatever tool gets the job done. I get the purist argument, that it can flatten things if you just slap it on, but like you said, it saved your painting. Sometimes you just need that quick color harmony. I've used a gradient map to fix a muddy forest scene by adding a cool blue layer for shadows, and it pulled everything together in two minutes instead of repainting for hours. If it looks good in the end, who cares how you got there.