For me: Voting represents support for both the process and the government that results from that process. By voting you are essentially expressing that you submit to the electoral process as the sole means for the exercise of political power. Even if you don't like the results, you've agreed to accept it because the rules are more important than the results.
Some obvious problems with that: What if the process itself isn't fair in the first place? We don't really get to choose our leaders. We get presented with a set of options which are acceptable to capitalists and are asked our opinion on which we like more. You could write multiple books on the ways the US electoral process has been structured to disenfranchise people and reduce the impact they can have on their government, but fundamentally it comes down to the fact that the government doesn't represent people and that's a feature, not a bug.
So we end up with a pair of awful candidates who both have done and will do more awful shit. If the election randomly fell out of the sky without context, sure, you could argue about one being technically better than the other. But it didn't. It's this way for a reason. It's this way because people are willing to cede their expression of political power to it despite the fact that it's clearly unaccountable to them.
Voting is just supporting the system that's deprived us of any real democracy while normalizing fascism to protect itself. Voting is a fairly low information form of political expression. You don't get the choice to be like "Oh I'll begrudgingly support this candidate, but this this and that are things I don't like and want them to change." You get two boxes. Each one represents EVERYTHING the candidate stands for plus the implicit choice of accepting the process in the first place.
If people want things to get better, they have to organize and take real, tangible actions rather than just begging capitalist politicians to do stuff for us every 2-4 years. People should be doing this regardless of who's in office, but let's put a fine point on it: People are worried that Trump is gonna be fascist, take away people's rights, and end democracy. Are you just going to accept that because he won the election? Are the rules that bind the process more important to you than the results? If not, you should be willing to do what it takes to stop him instead of chastising that people didn't show up to participate in a sham of an electoral system.
For what it's worth, I actually did go to the polls to vote specifically on an equal rights ballot measure in NY. At least that has a semblance of direct democracy. There I'm explicitly saying "I support this policy specifically" instead of supporting a candidate who just says they support those things while also doing awful shit. It passed, so that's nice. If anything I'm more pissed at Californians for voting against a measure to END SLAVERY than I am with people who didn't want to vote for a person currently engaged in supporting a genocide.