But who is "we"? The nominating process is an internal matter of each party, at least in the US, so it would be up to the members of the Democratic party. And for now, they're voting for Biden and Sanders in that order.
Well if you want to talk about the pillar of mediocrity, look no farther than Trump.
His famed "business acumen" is mostly bullshit. If he'd just stuck the money his daddy gave him into a low-fee market fund and left it there he'd be more wealthy than he claims. As for being a "real estate mogul," he's kind of a joke in the New York City scene. "Oh, but he was a wildly successful TV star!" Not hardly. The Apprentice made a splash at first, but it faded to middling status after awhile. Friend of mine was on season six, and it was on life support then. It was reinvented (not by Trump) as the "Celebrity Apprentice" and honestly the celebrities were not exactly A-list people. In fact the show recycled other reality "stars" to shore up the cast in later seasons.
"Joe Freakin Biden" has been a US Senator for a long time, was Vice President, and has a wealth of experience that Trump couldn't buy even if he was as rich as he thinks he is. And again, he's not.
If your measure of "who should be President" is sheer wealth, then Bloomberg is quite literally 54 times more qualified than Trump. Money aside, most of the Democratic contenders are more accomplished than Trump. Warren is a respected Harvard professor. Trump got into school because of his dad. Mayor Pete was a Naval Intelligence officer. Trump had "bone spurs." Steyer actually made his money. Trump failed upwards. I'm frankly at a loss to understand by which metric Trump isn't mediocre.