Same as several above comments, I definitely think it's okay as long as it's not too frequent and used in a smart way!
I try to straight up copy-paste pretty infrequently but there are definitely some times where it comes up in my art. For example, if there are 2 or more panels where the characters are in the same places with minor changes, I'll usually copy the image and make the necessary adjustments. This set of panels from my first comic is an example (and even one where I was inking traditionally, so I used a light box to transfer the images over xD)
This is another example from a newer comic of mine where the background base throughout is the same (although shifted slightly) and much like in animation, I used the faint sketch of the character in the previous "frame" to inform where to position them in the new one:
Lastly, although the first two examples had panels that were right next to each other in the reading order, sometimes I do reuse backgrounds and stuff spread apart. For example these are all the same background, but there was 2 or 3 panels between these two:


and another... like 3 or 4 between that 2nd one and this one:
Again, all the same base image but with slightly different zooms depending on what the panel needed, and different other stuff going on in each panel.
Saved a lot of time and I don't think the copy/paste police are going to be busting down my door... hopefully 