> - you need to be a fellow voting systems nerd to understand when you may want to vote tactically in RCV, so approximately zero people will vote insincerely

I don't think this is true. Consider a hypothetical voter whose sincere party preference order is "Constitution > Libertarian > Republican > Green > Democrat > Socialist > Communist". It doesn't take very big of a logical leap to say "it basically always seems to be a Republican or Democrat who wins, so for my vote to count the most, I should vote Republican > Constitution > Libertarian > Green > Socialist > Communist > Democrat."