I'm sorry that you think actually-murdered Gazans versus hypothetical future murders aren't "realities" to be considered, just principles, or that you think choosing between 2 people who both profess backing policies that will result in said murders, is a normal choice to be making as an electorate.
Trump should already be in prison, for any number of crimes. So should Biden. That neither are, is an indicator of how "well" our system is working.
There is a fine line between "working from within a system to change it" and "validating and reifying the system, by being a willing participant". If you are finding that your participation is not having the impact you intend, perhaps you should consider what side of that line you're actually on?