The path to a viable third party presidential candidate has to pass through the down ballot races. If you want (for example) a future green party or libertarian president, you need a bunch of governors, senators, and representatives first.
Third parties struggle to get on presidential ballots because they are ineffectual on a national scale. They’re ineffective on a national scale because they barely exist in between presidential elections.
Expecting to change the political landscape from the top down is misguided and unrealistic.
One of those exceptions is to be 65 years or older. Guess who that disproportionately benefits?