the only way to Democrats made their way back to the whitehouse was with an entirely new generation/brand of democratic politics under Bill Clinton, which embraced free trade and deregulation (i.e, the "third way"). So far, progressivism has not won in the way that this new brand of liberalism has.

This is a little too simplistic. First, it's important to note how weird the 1992 election was. It was the first time in modern history that an independent candidate had a legitimate shot at winning; in fact, Perot was leading in the early polls, and very well could have taken the presidency if he hadn't mismanaged his campaign, dropped out, and then re-entered the race. While he was somewhat centrist, he held a lot of populist and progressive positions like Medicare for all, assault weapons bans, opposition to NAFTA, and criticism of Reagonomics. Clinton ultimately won, but that probably had more to do with the 1990 recession than anything Clinton did, and, again, he very well could have lost to Perot's platform had Perot been a more competent campaign manager.

As for the failures of the progressive message after that point, I don't think that's true, at least when looking at Presidential races. Obama governed as a centrist, but he campaigned as a progressive, promising Wall Street regulation, home owner bailouts, and universal healthcare. He abandoned all of those goals early on, but they are still what got elected, and he even made income inequality the focal point of his reelection campaign (which he again abandoned immediately upon reelection).

While Biden would never be called a leftists, he was a savvy campaigner, and he correctly read that the country wanted a progressive candidate in 2020. He leaned heavily on his strong pro-union history and had Sanders help him craft a highly progressive platform to run on. To his credit, I believe Biden did earnestly try to pass that platform, and it's failure wasn't do to a lack of desire. (He also funded a genocide and refused to step aside despite his advanced age, so fuck him, but the point is he got elected on a progressive platform).

Now let's look at the presidential losers. Al Gore, a centrist technocrat, lost to Bush (sort of). John Kerry, a moderate war hero, lost to Bush. Hillary Clinton, who made the centrism of her husband's presidency the cornerstone of her campaign, lost to Trump. And Harris (who, granted, was cobbling together a campaign at the 11th hour) ran a campaign of tepid centrist reforms and lost resoundingly to Trump.

So, tl;dr: Bill Clinton was the only candidate who won on an openly centrist campaign, and that was a very unusual election. The two other presidents, while also being centrists, won in progressive campaigns, while explicitly centrist Democrats lost.

You gotta have the poors for that full-on capitalism experience. And it’s not complete until you demonize them.