You make a lot of good points. However, you should do more research about ranked choice voting, by which I’m sure you meant instant runoff voting, since ranked choice voting is a broad category and instant runoff is the specific method being advocated by the Green Party and a few state chapters of the League of Women Voters.
Claiming that Bernie could have “informed voters about the need for ranked-choice voting” shows that you are probably unaware of the many profound flaws of IRV. I say that because one of the worst outcomes of an IRV election ever was in the Burlington, Vermont mayoral race of 2009. This was not an isolated case, and it has been shown by multiple mathematicians that IRV is going to predictably often produce ridiculous results like that one, in which the least favored candidate of the three major contenders won the election. Burlington wisely voted to stop using IRV, having experienced first hand how bad a method it is for choosing political winners.
In fact, IRV harms third-party candidates more often than mainstream candidates, so it makes no sense that the Green Party, of which I am a member, supports it. And it makes no sense that Bernie Sanders would have seen any reason to inform voters about any supposed need for IRV, when he is certainly aware of how bad it is, given that he was, himself, a Burlington mayor. http://rangevoting.org/Burlington.html