I find it snarky and insincere when people conclude that Bernie is the only good option on the basis that Biden and Trump are basically the same.
The #1 platform item this year, by far, is Beat Trump. I don't think nominating a guy that a lot of difference making voters have a distaste for is the best way to achieve that. (See Hillary Clinton, e.g.) Further, part of what difference making voters don't like about Bernie is HIS PLATFORM. It would be rough ridin' stupid as eff for Biden to adopt it.
There's literally not a single person on this board who thinks "Bernie is the only good option on the basis that Biden and Trump are basically the same." You are presenting a false choice. I can reject both options without seeing them as equivalent.
There are people, lots of them in fact, that think Biden represents the smallest step forward you could possibly have. He's the one running solely off of what Obama did, not even attempting to distinguish himself in the smallest way possible. The distinguishing components of trump and his presidency are how his lack of moral compass seep into governance when it is impossible for others to get in his way. I think Biden's team handles the COVID response differently, but it certainly isn't outside of the realm of possibility that he would have taken a head-in-the-sand response, he's done nothing in his political history or in this current campaign that would allow anyone to think he would be proactive and progressive in his response.
I'll also point out that no one here has suggested that the Democratic Party adopt Bernie Sanders' platform, whatever that means. The Democratic Party should absolutely adopt a more progressive platform than they appear to have right now, it's literally the will of their voters. Democratic voters have shown that they like the progressive agenda, they just don't want it to come from an old, a woman, or a person of color. Biden is in the position he's in now because he's an old comfortable shoe.