I think one of the biggest strategic mistake 3rd parties tend to make in the US is trying to go straight for the presidency. That will never work, even if you have the greatest candidate ever and the best platform ever, which of course none of them do.
You need to build from the ground up, over a period of time. You need to start basically at the local level, show that you can be trusted with that, over time win some more elected positions, etc. Eventually, make your way up to the federal level, starting with the house. If things go well, and you get a respectable number of people elected there, you can move on to the senate. Eventually, once you've had a good number of people elected to somewhat important posts, and have shown that you can be trusted with holding power, over at least a couple of decades, you can maybe have a shot at pursuing the executive branch.
None of the 3rd parties seem to really understand that. No one is going to give the highest office in the land to a party with no real track record at the federal level. At least Johnson seems to understand that he's not going to win, and seems more interested in raising the party's profile over time.
Edit: For example, looking at the US Libertarian Party's wikipedia page, they have no one currently elected to the federal senate or house (which we all already knew), and no one elected as a governor, or to any state's upper house. They have one person in a state lower house. That's one elected person out of 7916 elected positions. That's not a party that's ready for the big chair.