If you are suggesting not voting then that has no impact and neither does 3rd party.

That's based on YOUR perspective. If your goal is simply to win every election then you are correct, but if your intent is to show that you will still vote, but not for the candidates or platform that the mainstream establishment is proposing to you than voting third-party is far better than not voting. Additionally, if people actually acted less defeatist before caving to the establishment and instead voted for a third party, then there would be a far better chance of the third party getting traction as the Democrat party Absorbs the Republican party.

Also, depending on what you want, voting for a third-party candidate may just better represent you. That''s more than enough to vote third party. The absolute bare minimum political action you can choose to express your political values is to vote. Actions tend to speak louder than words, anyways. When people fail to do that, then It's clear that they don't even know what they want.