If you actually work through the game theory, you find that single-winner instant-runoff voting is nearly as vulnerable to Duverger’s Law of two-party domination as plurality voting.

https://www.electionscience.org/voting-methods/runoff-electi...

There are much better single-winner systems available: see approval voting, score voting, and Condorcet voting. But if you want a legislature with proportional representation, you really need a system with multi-representative districts.

As the sibling comment from anderkaseorg says, IRV is one of the worst single-winner voting systems that isn't plurality voting.

Third parties would greatly benefit from range-voting[1]. I used to favor Condorcet voting methods as an improvement over plurality, but now I favor range-voting. Mostly for how much more straightforward the vote outcomes are, and the simplicity of explaining it. The no-show paradox inherent in Condorcet systems also bothers me[2].

There is a good summary of the properties of different voting systems on wikipedia[3].

[1] https://www.rangevoting.org/

[2] https://en.wikipedia.org/wiki/Participation_criterion

[3] https://en.wikipedia.org/wiki/Comparison_of_electoral_system...

agree - voting system is only 1/2 of the pie - the other piece being the actual governmental structure.. when parties not candidates are voted for, and coalitions have to be formed, the need to heavily fund 'magical individuals' is less, and the need to compromise between parties and meet people directly on their own terms increases..