As has been famously stated, democracy is the worst system, except for all of the others. I think people often underestimate just how bad it is.
The need for any sort of alternative system to first-past-the-post should've been plainly obvious in the '00 election. The problem is the people that could change that were elected under a first-past-the-post system and don't want to lose their current advantage.
I've seen discussions around how it can be more confusing than the current system, and can reduce confidence in the election.
The 2022 Alaska election was a great example of it failing: https://realrcv.equal.vote/alaska22/ FairVote called that election a success because people managed to fill in their ballots, even if they didn't get the outcome they thought they were voting for.
Definitely changed my mind over RCV vs STAR. Although I'll still support either if I had the opportunity.
American democracy. Other democracies have multiple viable parties and candidates.