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I assure you that you did not read any regular member of this forum saying that I-80 is boring. Such a statement goes against the founding ideas of RTA and what makes a great roadtrip and even more to the point it's simply not true.

However, if you are planning to go up to Yellowstone, then it would likely make sense to continue east on I-90, and head across the Black Hills, Badlands, and small towns of South Dakota.

But as Lifey mentioned, those are just a few of the thousands of things you could do. Rather than focusing on route numbers, I'd focus on the places you most want to see, and once you have an idea of your own must sees, then the route will start to build itself.