The world is full of nuance. Just like whataboutism and "both sides" can be convenient rhetorical devices for people lying to themselves or others, accusing someone of either can be a convenient figleaf for avoiding thinking about the flaws of one's own side.
The fact that Trump won in 2016 obviously overshadowed many things about that election. I didn't vote for him but I can still remember acutely the disappointment I felt during the primaries when the presumptive frontrunners were another Clinton and another Bush. Like out of 300 million people, these will be the choices presented to me? Whataboutism is bad mkay, but two things can also be true at the same time. Nuance.
Trump is exceptionally corrupt, pliable, and stupid. You don't have to like Harris to want to keep someone openly corrupt out of the White House.