I didn’t think Hillary Clinton was a particularly compelling candidate in 2016. But I wouldn’t have considered Biden am improvement, and didn’t regard him highly in 2020 either. He is essentially a superannuated barnacle on the body politic, consistent only in his ability to be wrong on foreign policy and military issues and his slavering devotion to his state’s banking industry.
Even if I were inclined to vote for Democrats, which I will freely admit I am not, I think the party can do better than either of them (or, indeed, Kamala Harris, who until the party needed her to step up was routinely dismissed as a plainly unserious and insecure politician who burns through staff as they contend with her weaknesses and personal abuse.)
Fighting the premise of the OP, IMHO the biggest issue with a 2016 Biden run is that Biden is overly cautious. This not only explains why he didn’t run in 2016, but also why it took him to long to declare his candidacy in 2020, his hesitancy with various forms of support for Ukraine over the past 2 years, and so on. Had he overcome that natural caution, I think he would have similarly been hesitant to attack Trump on what are his now obvious authoritarian ideas.
In other words, I think Biden would have done worse against Trump than Hillary did, mostly due to what seems to be an overly cautious personality. He wouldn’t have had it in him to go after Trump as aggressively as was indicated during the 2016 race.
IIRC he was also mourning the loss of his son, Beau. IIRC I recall reading he paid extra for his son to have the best doctors and the Obamas offered a free loan to Joe and Jill. I could be misremembering. Deep down Biden is still stricken with the loss of Beau. He lost 1/2 of his family decades ago if you recall. His firstborn daughter and his late wife in a care accident, left raising 2 boys until Jill entered his life.
Biden fundamental advantage was that he’s a man, and was therefore more electable than Hillary Clinton. I’ve always believed that a major driver behind Trump’s support was collective rage among much of the US populace at the thought that a woman dared come close to actually being elected President. So a proud “pussy grabber” and general misogynist was put into office as a collective slap in the face of the women of America, a way of demanding women that they shut up and submit.
Biden running would have reassured the bigots that it’s back to having white males in charge.
My take has always been that Hillary and her supporters felt strongly that she’d been done dirt by the Obama phenomenon of 2008 eclipsing her Glass Ceiling Campaign, and that it was “her turn” in 2016. Obama had shattered a different ceiling in 2008, so they couldn’t really bitch too much, but she and they felt entitled to the Dem. nomination when his eight years were up. She’d been a loyal Dem, serving in his cabinet, and she and they felt she’d paid her dues and then some. I think Obama himself probably felt some of that pressure, and wanting to avoid a bitter Battle of the Genders within the party, threw his support to her. A lot of Dems, including me, who didn’t even feel that strongly positive about Hillary personally, wanted to avoid an unnecessary and downright stupid “You’re against her just because she doesn’t have a penis” fight.
If I’ve learned anything from over a decade of these political threads, it’s that a large majority of people (yes, including the majority of posters here) fundamentally cannot understand much less accept the concept that other people do not think the same way they do.
And so conclude that even people nominally on the same “side” expressing a different opinion must have nefarious purposes for the disagreement instead of, ya know, legitimately having an opinion different from their own.