As shitty as it is, this country 1. Isn't designed in such a way that would allow a third-party candidate a genuine chance of winning and 2. Has too many centrists that will vote for Biden regardless. Trump has repeatedly garnered heavy support in Republican polls, so they're pretty much almost all in on him. Splitting the blue vote between Biden and whoever else will only lead to a Trump victory after which we might not even be ABLE to vote in 2028.
I'm legitimately having a panic attack. These airheaded anarcho-kiddies are genuinely going to land us all in camps.
biden's doing literally nothing to stop states from criminalizing lgbt people's existence 
their fears about a trump presidency are valid but i wish these libs would stop putting their hopes in the DNC when its clear they have zero interest in running a candidate that isn't complete dogshit
People are short sighted generally. If something doesn't effect them currently or the effects are said to be far off or only in specific circumstances it's sort of normal to go "ok, that sounds not good... but if I don't go to work right now I'll miss rent. I'll come back to that later." And they never come back to it for whatever variety of reasons from exhaustion to some sort of mental block on wanting to read horrible shit.
The solution for this short sightedness is having people whose entire job in life to bend society in a way to avoid things like climate change or to maintain rights like abortion. The problem with that in a capitalist system is avoiding negative effects of climate change might not be profitable. So that person, to whatever extent they exist, is ignored and undermined. We end up with this totally alienated population of people who broadly do want abortion to be legal, who do want to force corporations to reign in carbon emissions to avoid further catastrophic consequences in the climate but they lack power. Everyone is distracted by their own bullshit, all this abstract (to them) stuff about dying due to no access to abortion is driven to the fringe of the consciousness. The worse everything gets, the more it feels bad to think about climate change or starving homeless or whatever else. Simultaneously people are having their housing security threatened by raising rent, raising grocery prices, etc. It's all just shoving people into shutting down, ignoring, and just letting hell wash over us all.