Well, I used to think so too. However, at the height of the "Oprah for Pres" mania she is really only 10 points ahead nationally (and 60% don't think she should bother), which is where Hillary was at one point. Trump has maintained his following and that will never change, add in the hidden vote and Trump is closer than polls indicate. So, the only thing that can logically happen, is Trump closes the gap. Celebs and women love her - I get that, but more people than expected have come out and said "Yes, we love Oprah, but we wouldn't want her as president" - as they should. She may secure the democrat strongholds like California and New York...Chicago. With the tax situation and job creation going the way it is, working people and women may love Oprah, but they love jobs, money, food, investments and a roof over their head even more.
As I said, Oprah has never been in a situation that she didn't control and I think her brand is actually more important to her than anything else. She wont run, but I'd love to see it!