In the US, a representative democracy, people typically want to vote for a representative (here the Pres.) who shares their views on issues. The US isn’t going to have a national referendum on Gaza where the people can directly vote.
What ever your view point(s) your time to vote on your issue(s) is during a presidential or midterm election.
Because most haven’t I will actually answer the call of the question. Voting is perhaps the most important way one can voice their opinion. And carries more effect than most words the average man or woman can utter.
The largest argument against these types of stances is that it will create a spoiler effect. This usually operates on the premise that a vote to a candidate is owed and not earned and or that it is impossible to achieve a different outcome besides one of the two establishment candidates. This second premise being the results of people who decry voting 3rd party as useless based on a restriction with no physical or legal basis imposed on our society by our society. There’s nothing stopping people from electing anyone else on the ballot.
If you can acknowledge that we as a society have this power the idea of accepting a lesser evil is weakened. If you vote for a lesser evil you perpetuate the broken system you hate. In your example Gaza, if someone feels that the issue is so important it merits a principled stance how can they not take the stance?
It’s a matter of pragmatism vs principles.