Unless you can build a movement that outperforms at least one of the two current options from jump, you're going to get marginalized like any other third party initiative.

Lib Dems and UKIP in the UK shortly became relevant a few elections ago, and it caused a lot of raised eyebrows. Now they're firmly on the sidelines again, even with Labour in crisis over the past few years. The system just went back to a two-party equilibrium.

I don't think the lack of parties is the problem.