But all the voting methods have glaring problems, and every method is going to result in people complaining after their preferred candidate loses but would have won using another method.
RCV isn't going to poison the well any more than other systems. STAR voting and approval voting, for example, open themselves up to the criticism that voting itself becomes a subjective process, which could "poison the well" even more. When people have to worry about what it means to give a 3 vs a 4 to a candidate, or whether to approve 1 or 2 or 3 people?
Ranking candidates is an objectively accurate statement of preference (in contrast to STAR/approval which are subjective), and while instant runoff isn't perfect, it's easy to understand and doesn't result in absurd outcomes or people not understanding how to vote.
You can criticize RCV for sure, but if you want to defend another method, you have to show how its drawbacks aren't even worse.