I used to be vehemently opposed to RCV; I'm still against it. It's leagues better than FPTP and my hope is that it opens the door for improvements like STAR or anything that can satisfy the Condorcet criterion.
Without tactical voting (and good information to support it) the first thing IRV does (along with most variations that in practice get the label "RCV", though of course this doesn't apply to all ranked methods) is to throw out the compromise candidate that everyone likes.
In the current situation, I am concerned that most people will prefer their particular flavor of theocracy to finding ways to get along (which they probably prefer to anyone else's flavor of theocracy). We already struggle with similar dynamics a bit, but it's the devil we know and I really don't want it magnified.
Essentially, any power-mad dictator and authoritarian regime has some variant of this argument. Yes, we love democracy and voting, but we definitely cannot let those kinds of people vote or get elected. You are just espousing the softer version still accepted in some countries of "yes, the voting system is not ideal but it gives our side an advantage for now, realpolitik always trumps democratic principles".
Getting a little more concrete:
Imagine a society split roughly evenly between 3 religions. Let's say 35% follow religion A, 30% follow religion B, 30% follow C, the remaining 5% belong to other religions or no religion. Approximately everyone with a religion (in our model; reality is more complicated but not sufficiently to make things inapplicable) prefers that society be organized as a theocracy according to their religion, would sufficiently accept secular tolerance, and violently opposes living under another religion's theocracy.
In this imaginary society, what is "the desire of the electorate"?
If everyone votes their honest maximal preference then the plurality says Theocracy A, which is violently opposed by 65% of the population! Picking secular tolerance over Theocracy A is not just something I (probably) prefer from the outside, but is actually preferred by the vast majority of the population over what IRV would pick!
When you take all those factors together, I think it's overall worse.
