It seems to be everywhere (even on the top rated comment here). Biden himself is dismissed as being not left enough by a lot the online population from what I can see.

Because he wasn't the the fashionable choice for Democratic nomination (Sanders) he's reduced to being just an old guy who isn't Trump but is in the right party without anyone even bothering to even read his Wikipedia page or look up some of his speeches on youtube.

He's a passionate politician and an empathic speaker who has the experience to be a realist and appeal to republican voters too. He's exactly what is needed right now.

Sanders wouldn't have had a chance to get in, but even if he did he would just polarise things even further.