FPTP has more failures than IRV in general, they're just less visible because you don't have the ranking data to work out the hypotheticals. That may be good for FPTP's popularity, but doesn't make it a decent voting system.

FWIW I also disagree with the suggestion that people can't handle it. Plenty of countries use ranked or proportional voting systems and their citizens understand how to use them just fine. They may not be able to perfectly optimise their preferences, but then they can't do it in FPTP either (and it's provably impossible to do so in every case whatever the voting system).