I have to spend a tremendous effort to even get enough relevant information about the candidates to make an informed decision

I waffle about this a lot.

Sure, one effect -- perhaps even the overwhelmingly primary effect -- of my vote is to influence which candidate gets elected, and to use that power responsibly I have to know enough to decide which candidate would be better to elect, which requires tremendous effort. (Of course, that's only an argument for not-voting if responsibly using my power to not-vote doesn't require equal knowledge/effort, but either way that's beside my point.)

But another effect is to reward or punish campaigns, which has an effect on the kind of campaigns that get run in the future, and it often seems to me that this is worth doing and requires less knowledge to do usefully.

Of course, the magnitude of the effects in question are so miniscule it's hard to care very much in either case.