He gets to balance the power of Congress. He can refuse to enforce their bullshit. But more importantly he's the leader of the Democratic party. He has massive influence on the direction the party takes, and can put pressure on members who get out of line.
I think most people are done with people who try to "work within the system set forth by our behind the scenes over lords"... We want someone who's going to call them on that crap constantly and fight against it with every move they make. Biden is clearly not doing that.
I actually got heavily involved with politics after Bernie. Including running for office in a very red district where I had no chance of winning (just happened to be where I was living). Turns out, the establishment would rather reject anyone left of them and lose to Republicans, than to move an inch to the left and anger their masters