Having people disenfranchise themselves based on whether or not they feel they have an adequate grasp on the real issues would not end as you'd hope. Are you familiar with the Dunning-Kruger effect? If people took your advice to heart, the likely result would actually be a less-informed electorate: the only people who would actually disqualify themselves would be the only ones thoughtful and self-critical enough to countenance the possibility that they weren't qualified.

There is no principled way to distinguish between a vote based on propaganda from a vote based on knowledge that doesn't actively disenfranchise voters. So why even try? Just vote your say, and rather than expending your energy trying to keep people out of the ballot box, expend it on educating them.