I guess it's fine to be responsible for letting the greater evil into power as long as you can tell yourself that you were morally correct at the end of the day. Because that's what you're doing. You're making a selfish moral point, and in turn actively increase the odds of a worse outcome. You feel better about yourself at the expense of everyone (including yourself).
Because what do you even gain by not voting here? The moral high ground? You just make it look like the greater evil is more desirable. At least spoil your ballot, so that it counts in the percentages...
I'm fine with people who don't care about politics. I think they're missing out on having their say, but I get it. However I will never understand your mindset.
You claim that participation legitimized the false choice, giving the lesser evil no incentive to reform, yet this is just wrong!
Voting for nobody means the status quo sticks. Voter participation can drop insanely low, and still nothing will happen. You're just giving more power to those who do vote. The lesser evil has no need to change their ways, because you are irrelevant to them. You are not part of the equation for them. You are, quite simply, nothing. You may as well not exist. Your voice isn't being heard, because the only time your voice matters in the US is when you vote. If you don't vote, you have no voice.
But if you vote for the lesser evil, you are now a threat to the greater evil. The greater evil must now start leaning towards policies held by the lesser evil party in an attempt to take votes from the lesser evil party. By doing this, the lesser evil party once more must distinguish themselves, and thus they will move further away from evil in an attempt to keep your vote.
Voting for the lesser evil has a chance of improving the country. Not participating guarantees the opposite.
And all of this is ignoring the short term effects of how one party is definitely more evil than the other. One of them is actively trying to make the system worse, and less democratic. Ignoring that fact is so strange.