Ranked choice’s end results are not the issue. It solves the problem because it allows multiple similar candidates to compete, which means the left wouldn’t have needed to winnow down to a single candidate. If Biden becomes incapable that’s fine, people have another candidate already available who wasn’t spoiling him by existing. And if we don’t all agree that Biden is incapable? Biden-stans can vote him first and the other candidate second, and vice versa, and one of them will garner the full vote of the left.
What kind of nonsense question is that? These candidates both don’t have near majority support (polls of head to heads are not measuring that) and there’s no reason to have a different system if two hypothetical candidates actually did. Most people did not want this rematch in the first place.
If you have a situation where say there appeared to be two likely dominant candidates, but one crashes and burns spectacularly, other voting systems wouldn’t cause a default decision for their single opponent. And the people who thought Joe Biden was too old from the very beginning could already be supporting their replacement. Hell, we could just have all these potential replacements already competing and work it out in voting.