@Gameface essentially, yes a younger, more liberal, more diverse, candidate can win the primary. The question lies on if they can win the general? The general is where things become difficult as general election voters tend to be older and more moderate ideologically than democratic base voters in the primary.
This will be especially troublesome since Democrats desperately need to win rust belt states, and those states are trending red.
So the question is, do you go with a younger candidate who might be more liberal ideologically? Who might be gay, a woman, or black? Because they might turn off some general election voters. Sure, you might juice your base but no one cares if you win the popular vote by millions fail to reach 270 EC votes.
This worked for Obama but didn’t work for Gore, Dukakis, or Mondale.
-OR-
Do you go for someone old and moderate and hope that you get 270 by appealing to moderates but risk depleting your base’s turnout?
This worked for Bill Clinton and Joe Biden but didn’t work for Hillary Clinton. And had Bernie been the nominee in 2020, I think it would’ve resulted in a Trump re-election. Way too many general elections voters would’ve been spooked by democratic socialism.
Republicans don’t have to worry about this because they’ve given up going for the popular vote. They’ve found that they can juice their base and their base is good enough to win enough EC votes. The EC actually favors rural less populated states. That’s why Bush won in 2000, why trump won in 2016, and why trump was close to winning despite losing the popular vote by millions in 2020.
So we probably will see younger candidates in 2024 if Biden doesn’t run. It’d be hard to find older candidates! But there’s a real dilemma facing Dems since a candidate might be extremely popular for them in the primary and might be more popular nation wide, might be completely unpopular in key EC states for the general and cost them the White House.