So why argue against people trying to get a better candidate?

Because I don't believe you are trying to get a better candidate. I believe you are trying to attack Biden so that Trump wins. Your arguments are ridiculous and nonsensical.

1. You and everyone else willing to vote for Biden, will vote for any Dem.

I already answered this one. I don't believe it is "and everyone else." I'm only speaking for myself.

2. Some people don't want trump, but won't vote Biden.

Yes, some people don't want Trump but won't vote for Biden. There are more people who won't vote for someone they don't know. I don't believe the former group outnumbers the latter.

3. There exist other politicians who can be the Dem nominee.

No, there are no other politicians who both can and want to be the nominee right now. None.

Conclusion: Sticking with Biden, becomes the worst chance at beating trump.

You only reach that conclusion if you want Trump to win.

Don't worry about anything else, just look at that logic.

Can you find any flaw in it?

I cannot find any logic, so I also can't find any flaws.

But just so you don't keep asking:

I’m curious, though, who is your candidate?

AOC

This reveals you aren't serious at all. Every progressive would love to see AOC in the White House, but no true progressives are delusional enough to think she shouls challenge Joe Biden for the nomination. AOC has no interest in running for President, and has zero chance of raising the money or infrastructure required to mount a legitimate campaign. You might as well have named Jon Stewart or Kermit the Frog.

But again. All we're talking about who can beat Trump. And if that logic up there isn't something you disagree with, let me know. Just stripping this all down to a pure logic thing.

Again, no logic, just distractions.

I'm optimistic this will work.

I don't believe you. But if you're serious, grow up.