I keep reminding myself that the biggest difference between 2016 and 2020 is, in fact, the candidates.
Donald Trump was an unknown political entity in 2016. Hillary Clinton was well-known and had high negatives. So virtually all the late-breaking vote went the way of the new guy, as did most of the vote that was polled as third-party and changed their mind in the last few weeks. It was enough to tip Wisconsin, Michigan and Pennsylvania (I'd argue Florida, too).
DJT is no longer an unknown political entity. In fact, his negatives are now at least as high as Clinton's were. Biden has nothing like the negative polling of those two. So, it comes down to turnout. Dems vote, they win.