4 years ago, Democrats said the border wall was stupid and bad. They said that Republicans were racist for claiming all Mexicans were drug dealers and criminals. Today, Harris is saying she's gonna build the border wall, be tough on migrants, and has basically adopted Trump's policies on immigration.
There is no indication that the Democrats will not be just as bad as the Republicans on Israel in 4 years.
To address your second point "not voting for Harris is a vote for Trump"; why isn't the opposite true? "Not voting for Trump is a vote for Harris", follows the same logic, so refusing to vote or voting independent should be net neutral, no?
This election should be a slam dunk victory for Harris. The data shows that adopting leftist progressive policies is popular. Biden dropping out resulted in $4 million in small donor fundraising. Picking Walz resulted in another $2 million. People got really excited when it looked like the Democratic party was making leftist progressive movement.
Since then, the Dems have been aggressively moving towards the center. More lethal military, inciting panic about the border, ignoring Palestine. This has resulted in an extremely tight race as people are no longer excited to vote for Harris.
I want Harris to win. Moving leftward politically will attract more voters. Taking a firm stance on stopping the Israeli government's genocide is a leftist progressive policy. The bag is right there, she just needs to grab it.