Fwiw you should support IRV if you have to (if it's on a ballot against FPTP and is the only option), but it's basically the bare minimum acceptable voting system. FPTP is simply not democracy, but IRV is barely okay. Any single-winner system is inherently worse than a proportional system, because it can be subject to gerrymandering, and it's majoritarian. IRV might allow minor parties to exist without hurting their more-closely-aligned major party, but it won't do a great job of letting them actually get representation.

Take Australia for example. Our House of Representatives uses IRV, and our Senate uses the proportional system of STV. Our major parties are Labor (centre-left) and Liberal/National coalition (right). Our most noteworthy minor party are the Greens (left). The Greens consistently get about 10%. In the House of Representatives, at the last election they achieved a record 2.7% of the seats in the Reps (their previous best was 0.7% despite over 10% of voters putting them first), and they currently have 14.5% of Senate seats, on the back of a 12.3% and 12.7% first-preference vote, respectively.

IRV helps, because it removes the spoiler effect in real-world scenarios. You should support it as better than FPTP if you have to, and not let the perfect by the enemy of the good. But it shouldn't be what you aim for in an ideal scenario.