It barely matters. Biden broke with decades of Democratic fuckery of the working class, and no one noticed. Everyone blamed Harris for all of Biden's decisions about Gaza, and no one really noticed or seemed to care that she hadn't been the one making the decisions. They just kept using the same messaging that she was supporting a genocide, unmodified from the form it had been in for Biden, and it kept working great. A majority of people were convinced that Trump would be better (!) for the economy.
The Democratic party definitely has an overall-shittiness problem, sure, and if you want to hold Harris responsible for any particular failure to break with that, I won't really stop you. But that wasn't what lost her the election.