A multi-party system would make some things better, for sure. But we will never get that, as long as alternate parties are laser focused on national wins over local wins. Without the groundwork laid at a local level, no third party will EVER get enough votes to unseat the Big Two. You need to show cities and states what your party can do for them BEFORE asking the public to vote for you on a national scale.
If third parties refuse to do the grunt work and build their coalitions like everyone else, then they deserve to keep failing.