> Sure, but then shouldn't the universal vitriol cancel itself out somehow?

It does, both sides got about the same amount of votes as you can see.

> It feels much more like the Democrats ignored (or were perceived to have ignored) a lot of substantive issues for a large section of the population.

I don't think so, it doesn't matter how much you try to do for people if you also namecall them at the same time, they will assume you aren't on their side even if your policies are better for them. Vitriol ensures the vote becomes tribal instead of rationally inspecting both sides and picking the better option.