Of course just because there are technically flaws, doesn't mean it's not an improvement over the status quo.
Instant Runoff Ranked ballots are particularly well suited for electing a single position like a Mayor or President. Given that it's still a majoritarian system like First Pass the Post, it's a much more questionable system to use for other things like electing a parliament.
I remember seeing a 2D chart representing voter preferences on the X and Y axis, coloured by who wins under those preferences (and some symmetry-breaking assumptions). Some systems showed clear biases towards certain outcomes. IRV had a pretty symmetric shape but with a splotch in the middle that was a random jumble of different colours - an unpredictable, chaotic outcome.
Preferential/ranked choice voting allows people to vote third-party while still expressing a preference for one of the majors.