I think people often dismiss systems like STV/IRV by essentially saying "Arrow's theorem implies you can still vote tactically, so it's just as bad". But there's a big difference: in STV it's much harder to figure out how to vote tactically.

In First Past The Post systems, tactical voting is blindingly obvious: if there are two candidates you like, but you don't think that your favourite has enough popularity to win outright, then you should vote for the other one, to avoid splitting the vote. This is easy to understand, and it's also easy to detect circumstances where it would be beneficial for you to vote other than your preferences.

OTOH, even though there are times where you can vote tactically in STV, they're harder to understand, and crucially, it's much harder to recognise such opportunities: you need a lot more information.

This means that, in general, STV would cut down on tactical voting a great deal, simply because it makes it harder.