I know a lot of people don’t like the American First Past the Post system, but to be honest, even in a proportional system like here in the Netherlands, you end up with very similar dynamics.
Truth is, progressives are always a small minority, in every country. Because they are always ahead of the curve on change.
In the US, this means that you only get a handful of progressives in the most progressive districts and never a really progressive national government.
In the Netherlands, this means progressives are always represented, but need to compromise to form a government. And often, they even get skipped and the centrist and conservative parties form a coalition.
Truth be told, Biden is as progressive as you could hope to get in the USA.
And, while I do think it is important to criticize him - and even threaten to not vote for him - to enable him to move more towards the left, it is also important to vote for him.
Progressives always win, not through getting majorities, but because they have the right ideas and eventually the other parties catch up to them.
For recent examples, gay marriage in the USA or marihuana legalization are now law in the USA.
I am 100% confident that American policy on Israel will also shift thanks to progressive voices. And it will not require a progressive majority.