The Proud Family had been on Disney since 2001. Frozone was a major character in 2004. Hercules' storytellers were all black if I remember correctly. And let's not forget James Baskett's award winning performance as Br'er Fox and Uncle Remus. The first Academy Award Disney would earn and it was a Black actor who won it.
Yes, Tiana is the first black "princess" and is a significant marker in representation, but we shouldn't forget about the incredible talents who blazed the trail prior. I always found it odd that Princess and the Frog presents a black character living in the 1920's South, but the only conflict which she meets is because she's poor. I get not wanting to delve too deep in a cartoon, but they chose the setting and the characters. It reminds me of Greatest Showman when Efron is reluctant to be with Zendeya during the Civil War, yet they refuse to say why his parents wouldn't approve of her as a person.