You're missing the point. There were only two possible outcomes: Democrats or Republicans. Both were bad and unappealing. Both are too dependent on the status quo to serve as vehicles for real change (so primaries are pointless too).
"More parties", through elimination of first past the post, absolutely changes things. It allows you to vote for someone who truly represents you and your interests without "throwing away" your vote. That's impossible today.
> There were only two possible outcomes: Democrats or Republicans
This is the civic illiteracy a higher comment refers to. Beyond the primaries, there are numerous down-ballot initiatives that don't tend to cleanly sort along party lines.
