Another problem with RCV is that it’s difficult to understand, at least when you get into the runoffs. That makes it harder for people to understand and trust the election system, which is also very important.
This is one big issue for me with IRV vs Cardinal systems. Both handle _weak_ spoilers but IRV doesn't handle ''strong,, spoilers. Understanding that these are two different types of spoilers is really important. It is "Bernie vs Hillary" and "Cruz vs Trump." Even with IRV we'd still see the parties trying to prevent strong primary candidates from running independently because they could spoil the election. With cardinal methods (approval, score, star) this is far less of a concern and thus I think more democratic of an election. I honestly think we should be much more concerned with strong spoilers than weak spoilers (weak spoilers don't affect elections much anyways).
STAR: 5, Score 4, approval 4, IRV 1, FPTP 1
It would be ranked in this order too, but there's more expressivity here than an ordinal system can provide.
FWIW, this already happens. That will also happen under any system. I'm not sure why you think IRV encourages moderates. It actually encourages extremist candidates which is why I'm particularly against it.