His presidency is regarded by the vast majority as lacking in vision and a clear lost opportunity to do something radical.
Oh yeah, he was the first black president...but more black people ended up in poverty after his time in office than before he took office.
Obama never ran on a progressive economic policy (he was pretty centrist if I recall). Also, the black-white wealth/income gap has been present for ages; it was highly exacerbated by the great recession in 2007 and has never fully recovered. Obama took office in 2008 and you can't pretend he can be blamed for the 2007 recession and its continuing consequences for African Americans.
Also, just to note, Carter was one of the most economically conservative, almost-right-of-Nixon presidents... He has this weird folklore surrounding him as if he was progressive and fought for the little-guy: he didn't. He waged a war on inflation that only increased unemployment and caused interest rates to soar, but didn't offer any tax cuts either; he favored deregulation and increased social taxes, and passed the Hyde amendment which banned federal funding for abortion. He passed up an opportunity get the government investing in renewable energy, thinking that private industry would do so by itself (it didn't). Etc.