Tl;Dr the election was the only place that we had to have that discussion.
Look, there was a primary in the literal sense, I voted in it, but there wasn't a primary in the practical sense. There were no debates, no discussion of his platform for '24, Biden didn't campaign, and the Democratic party / Biden Campaign worked HARD to shut down questions about Biden's viability or the Mandela effect where everyone seemed to remember him promising to be a single term president. I mean, I could swear I remember it too; I'm still puzzled about where so many folks got the idea. Then, once we were way past the primary, we found out that Biden was nowhere even near viable shape for the campaign trail. He put on the most disastrously bad debate performance in presidential debate history against an opponent that should have been (and was just four years prior) a joke. None of his other "see? He's fine" appearances before or after inspired much faith either. So, we basically ended up with Harris and zero discussion about her platform. At first, I was really excited and eager to see what her platform would be. As time went on, though, I started seeing more and more that reminded me of HRC '16 and less meat to get excited about. If there had been a real primary in a practical sense, I would not have voted for Harris (and didn't vote for Biden, I think I voted Phillips) on the platform she had.
The primaries are a time for the campaigns to work with voters and figure this stuff out, see what appeals to the base and is likely to get them to turn out. We never got to have that conversation with Harris, we barely had it at all with Biden. The only place we could have it is during the election, and my hope was (and remains) that campaigns are agile enough to respond when their base gives them feedback. I don't support the Democrats because they're Democrats, I support them because they offer the closest practical path to policies I want to see enacted. I want to see good policy win, and I think good policy will get the democrats their wins. We can't ever improve if we can't be accept criticism, and when it comes to politics, the appropriate way to criticize is a bit like finding the appropriate way to protest according to Fox News. We need to have these conversations to get better, and I absolutely do blame the Harris and Biden campaigns for putting themselves in such vulnerable positions and failing to respond appropriately to criticism. Their job is to get elected, and they failed.