Is there any solid reason to be against ranked choice voting? I’m honestly asking.

So it may depend on whether you're talking about single-winner or multi-winner elections. Ranked Choice voting can mean many different things depending on how it's counted, even more so once you get to multi-winner elections. (See, say, Schultze STV.)

(By multi-winner elections, I'm talking about things like "elect 5 members of city council".) Most commonly, for single-winner elections, people mean Instant Runoff. It's generally reasonable, but so is Approval Voting. For multi-winner elections, many options... most are bad.

I, and most of the smart political scientists I know, adore STV and consider multi-winner RCV (PR) their dream US reform. What don't you like about it? nytimes.com/interactive/2018… nytimes.com/interactive/2018…

Proportional Representation is not RCV. Each voter just votes for one party, and the parties are represented in proportion to their votes. I'd love to have the legislature be PR, or more likely MMP..

That said, I also would prefer nationwide MMP (like Germany or New Zealand) rather than the weird Spanish/Portuguese-style multi-member districts that the above article proposes.

The current nomenclature uses RCV as an umbrella; it refers to a system of ranking. To a elect a single winner, use the IRV algorithm. Not proportional. To elect multiple winners, use the STV algorithm, proportional, like Northern Ireland, Scotland, above article. Both are RCV.

I think MMP is a good voting system, but a much tougher sell in the US where people tend to dislike the parties and political association.