It's because our two party system (and our education system ...) doesn't allow you to have nuance or more than one or two issues that you vote on.
Criticizing Obama for drone strikes only ends up enabling the turn-the-middle-East-into-a-glass-parking-lot people (to bring back 2010 talking points). Similarly, to point out that Biden wasn't nearly tough enough on Netanyahu (he tried to grow a couple vertebrae of a backbone approximately twice) only ends up enabling the "Remember the Abraham Accords? Trump/Kushner a jew-whisperer!" argument.
I think Biden allowed genocide to proceed apace in Gaza. Full stop. This is just an attempt to answer your question about what would have been better under Kamala, presuming she would have been Biden 2.0:
Biden heavily pressured Netanyahu to open to border with Egypt to let aid in, even temporarily withholding military support to get him to do it. Additionally, Biden made an effort, however ineffectual, to airdrop aid and build a temporary dock to bring in aid on ships. Biden rolled over for Netanyahu, but there was at least the semblance that he was bothered by the civilian toll and attempted to lessen civilian suffering.