I don't disagree with anything you said, but my intuition tells me you're possibly under-estimating the proportion of voters who routinely vote against their self-interest without realizing it.
It wouldn't surprise me at all if that was >30% of voters. Assuming that number I just made up was correct, just for the sake of argument, the parent comment's question is very interesting: what does that say about voters' agency?
It's worth considering that you're not really talking about their own self-interest. You're talking about what you think they should want.
For example, anyone who likes the non-employee status of Uber driving will vote against it. Anyone who wants to be an employee is voting for lower wages, although higher benefits. They may prefer that, but not everyone does.
By that same token, we're all only talking about what people think they should want, and not necessarily what will really benefit them. By extension, the argument becomes that it doesn't matter how well people are informed, only that they act on the limited information they have. I prefer to emphasize efforts to inform the public better, rather than leaving them out to dry when their hopes are not reflected in the outcomes of such things.
I followed the news at the time, did you? Swaths of people who voted for Prop 22 were interviewed after it passed, and asked whether 1) they understood what was in the bill and 2) if they appreciate the changes that took place once it was in effect. The responses generally ranged from "I thought my job was going to get easier" to "I can no longer afford to feed my family".
at the point where there's a gov't agency that is forbidding free media from existing, or to censored to prevent the alternative argument.
Otherwise, the voters would not vote against their own interest (or if they do, it's deemed to be their choice to do so).