Even if you legitimately (and incorrectly) think that Bernie Sanders is some kind of a hero or a saint or a true champion for the people...
...he's just endorsed a racist, rapist warmonger for President.
That's how bad the system is. That's how absolutely shit-awful miserable your choices are. You can run from it by lying to yourself, by pretending it's not true, that Biden isn't any of those things, and that everyone saying he is just a "Bernie bro" or a "Russian bot," or you can be a fucking grown ass adult and admit to yourself that, vote for Biden or not, a system that consistently gives you these kinds of options deserves to be burned to the fucking ground.
It’s wild to me that so many Democrats just can’t bring themselves to vote for Biden and acknowledge him for the monster he is.
Maybe I’m wrong to think this, but I believe this indicates a lack of conviction and moral honesty. If one votes for Biden, while acknowledging him for what he is (a racist, a rapist, and a warmonger), then one is capable of condemning the system that forced this choice between two terrible options upon us, and resisting Biden in favor of better Democrats in the future. You can honestly say, “I vote for Biden to defeat Trump, and will vote for another to defeat Biden.”
If you can’t do that; if you lie to yourself, and insist that he’s not racist, not a rapist, and not a warmonger; then you can’t condemn the system. You are, in effect, saying “the system is fine, because it gave me a choice between a bad man and a good man.” What’s worse, is that you’ve removed a powerful imperative for you to support candidates who are actually good, and already taken the only step needed to ignore the crimes Biden will surely commit as President.