We are talking about American politics, so yes. Sorry but that's the reality.
Not only that but Harris does have an issue with her own image tbh. Normally the Vice President has 'a cause' to which they attach themselves and promote. Harris hasn't really managed to do this and the argument I've heard is 'what does she actually do, what does she represent and who is she really?'.
She's not really taken ownership of the Vice Presidency and 'made it her own' if you will. The argument is that she incredibly non descript and lacking in presence.
And she's going to go up against Trump. Perhaps this will work in her favour but I very much doubt it.
The US perhaps more than any other western country looks for personality and 'a strong leader' . That's particularly true for anyone who leans slightly right but potentially could swing left for the right candidate.
Historically the younger looking candidate has always won the US election - with two exceptions - the first is Hilary and the second is voting against Trump (I frame Biden's win in this way deliberately as he didn't carry enthusiasm - it's similar to Keir Starmer's election in that the main motivating factor was a vote for competency at the last election not voting for Biden).
You also have to factor in the mentality of Christian America which is deeply patriarchal to a degree that Western Europe finds totally alien. There are many women who feel strongly that their role in life is mother and wife before career. (Career women are a coastal thing and goes hand in hand with atheism which is also deeply associated with the Democrats).
It's women, much more than men who make up swing voters. Trust will be important. Do they think they can trust Harris with their daughters. So abortion rights and women's rights are going to be pushed really heavily if Harris gets the nomination. That may entrench and alienate a whole bunch of men too. And honestly, stuff like the Title X stuff is going to be problematic for Harris rather than a help. I think women voters will trust a male democrat more than a female one, if they aren't deeply associated with the likes of Dylan Mulvaney.
I actually think that being a woman is more problematic than being black when it comes to US politics.
I think Harris is a deeply problematic candidate, and that will be seized on by Trump and his team. He will be delighted if she is the Democratic candidate.
But I say all this, mindful I've not spoken to a single person including Americans who are staunchly Democrat who hasn't said Biden is past it, he needs to go and he can't win. Not one. That's the problem and the lens that everything must be seen through.