I think he would have won, although perhaps not in a landslide. But Obama is an excellent politician. He had the ability to convince people that he genuinely cared about their problems and wanted to solve them (largely because I genuinely think he did) even as inequality worsened.
Biden could do the same, and maybe he will. But I'm not hearing that message from him so far. His message is specifically anti-Trump, but I think the far better message this cycle is opposing all the things that Trump represents as well- the inequality of opportunity, the different justice systems for the rich and the poor, the general notion that the rich and powerful can get away with anything from from sexually assaulting women to giving themselves and their donors massive tax breaks to trashing protections for preexisting conditions because you don't like the name on the law that created them, while the rest of us are left holding the bag.
That's what the Dem midterm candidates did, and it worked out very well in the states that Trump turned from blue to red in 2016.