One of the results of long years of purging progressives from high office is that the Democrats have no professionals within the party popular enough to run.
Running Winfrey takes a page from the same Republican playbook that produced Donald Trump, Arnold Schwarzenegger, and Ronald Reagan, but that’s natural enough: if the party wishes to ignore the desires of its base, it has to make a show and hire a showperson.
I doubt Oprah’s draw would mostly just be that she’s not Donald, but of course it’s apt to be a personal rather than issues-based campaign. And the issues that will forefront would again be gender and race to the exclusion of matters economic class, corporate control, first and fourth amendment rights, and so forth.
Were Winfrey elected, other people would mostly run the country. This would presumably be more or less the team that was working with Obama, the Clintons, the Bushes, Ronald Reagan, et al. It’s not terribly relevant in terms of any sort of progressive agenda.