Maybe you would turn out to vote for positions other than President, but I fear a lot of people go to the polls during general elections specifically to vote on the President, and also vote for other positions while they're there. In other words, an attitude of "don't bother voting for the Dem candidate" would translate to fewer votes for everyone else down-ticket.
I'm skeptical that people are really awake and angry in any way that matters. There's a growing sense, I think, of general fatigue with nonstop crises here. Democrats are angry - of course they are - but moderates and compulsive centrists seem to shrug, consider this endless series of crises the new normal, and adapt without really caring enough to vote the GOP out. No matter how absurd the situation, if it sticks around long enough (like, say, eight years), people will just get used to it and think it's normal and acceptable.
That's just one of countless reasons a second Trump win would be lethal. His far-right agenda would, in time, be seen as center-right (it increasingly is already) or even "moderate."