I see the accusation of whataboutism more often used duplicitously to deflect from double standards or baselessly singling out one favored group to the exclusion of other groups caught up in the same problem.
Person A: "Group X children have falling test scores; we need to fix that."
Person B: "That's part of a bigger problem: there's a decline being seen in most groups of children, so this is probably a more fundamental problem than group X being neglected."
Person A: "That's whataboutism; stop trying to change the subject."
Or:
Person C: "Innocent people in group A are being killed by group B."
Person D: "Groups A and B are in a vicious conflict, and innocent people in group B are being killed also."
Person C: "Quit it with the whataboutism. You're just trying to make it seem like the innocent people suffering and dying in group A don't matter."
Though there are legitimate deflections when you fundamentally change the topic. For example:
"These oil spills are killing millions of birds a year."
"Yeah, but you're ignoring the millions of birds a year that are killed by natural predators."
That is whataboutism because it's an attempt to deflect from a topic over which we have some control to a topic that is much harder to deal with. Most accusations of whataboutism come from something different: an attempt to pretend that one group's problems or challenges are unique instead of being part of a bigger problem that affects many or most other groups and stems from the same factors. This is a kind of chauvinism that creates hostile divides between people and tries to establish "victim cred" as a mechanism of social and Overton window manipulation. It's generally very disingenuous and is much more about the boosterism of one group over another.