You're right about maybe having some impact on people's mindsets overtime if we can get some sizable percentage voting 3rd party but voting 3rd party is still a wasted vote with respect to the current election as it won't affect the results in any way. And it's worse than wasted if you're in a swing state.
The only way to show you don't whatsoever endorse not just the republican and democratic parties but the voting system itself which I don't is to not vote.
RE: A mathematical explanation how voting third party in 2016 is the only vote that counts