I will say I don't think we should completely discredit the fact that personal excitement is a piece of the puzzle, but let's hold off on the all out and doom and gloom
It's hard to tell from online vibes alone, but recent polling still shows Harris with an enthusiasm advantage (and Trump down from 2020). Also, Democrats and Dem-leaning Indies are overwhelmingly happy with her as the nominee, which was *not* true in 2020 or 2016 news.gallup.com/poll/651692/...
Harris is rated better than Trump on certain character aspects, including likability, while Trump leads on dimensions of leadership strength.
And young women are more revved to vote Harris. They, unlike most of their male counterparts, have real skin in the game. And are also less likely to loudly announce their voting intentions.