I just think even granting this framing, what is the point or the lesson here? Is the idea that Clinton in 2016 was more well-rounded, had broader appeal as a candidate and young people were too immature to realize this?
We do not need to start from the point of view that each given interest or group is totally opposed, that we are locked in some zero-sum death spiral where "the youth vote" shares absolutely no overlap with anybody else. Politics is possible at all because we believe in something else. You could decompose everything down into a list of people to blame with stuff like this, but it won't tell you what to actually do!
So it's better to treat them as a totally unreliable voting bloc that is nice to have, but in no way should be treated special. They are fickle, impossible to corral, and make particularly awful coalition partners.
Bernie, for one, would have done well to use their energy to launch, as he did, but then switch to broadening his coalition, rather than doubling down on catering to their every whim and attempted browbeating. That rigidity and tunnel vision is what sunk him, and is what would have led to total electoral collapse if he had somehow made it to the nomination.
But really, if you have a democracy where there seems to be one uncompromising bloc that no one can really satisfy, that too is democracy in action in a way! Or rather, it maybe says something about the state and the parties that this is the case with regard to the youth. Given all of history, we can't just say in general "kids are intrinsically uncompromising, short term idealists fundamentally incompatible with democracy." Right?