What is defeatist about it? It is about constantly participating in the system to make sure your views are still considered.
It means participating in primaries to make sure some of your candidates get picked even if others are going to lose. For instance, I’m going to vote in the primary because it will have a major impact on choosing a Senator of my state even if Biden is going to be the Presidential nominee.
It means choosing candidates in the general election that you can at least try to influence with protests and other actions after the election. I’d rather have a percentage of what I want politically done than nothing.
The alternative seems to be not to participate, which feels more defeatist.