Agreed, as with another commenter, that I forgot Citizens United.

As far as how ranked choice voting is an improvement is because it’s a much fairer way to do things. What I mean is that the way ranked choice works is you pick your first choice, then second, third. etc. Think of a primary. Let’s say you really liked Maggie Hassan but if she couldn’t win your next choice would be Bernie, and let’s say your third is Biden. If Hassan doesn’t get enough votes to win there’s an instant runoff and the vote you cast for her would turn into a Bernie vote. Then if Bernie couldn’t do it the same thing would happen and your vote would turn into a Biden vote. Now imagine your first choice is Bernie but you HATE Hassan. You’d put whoever else as your second choice and then if Bernie doesn’t make the cut you won’t have wasted your vote. It would go to your second choice, or the candidate who “ranks” second for you. The current system is how you end up with Biden and a ton of democrats saying they don’t hate him but there not thrilled with a lot of aspects of his presidency.

ETA: ranked choice voting would only really show its benefits with more than a two party system in general elections. Although, it would eliminate people getting mad at people (justifiably) who vote for small third party candidates which, in the current system, is like throwing your vote away.