Black people have had problems building wealth because we started from such a disadvantage, and we continue to operate under said disadvantage.
White people have been building and passing on wealth for over 400 years in America. Blacks folks have bad less than 50 years of somewhat equal footing(still not truly equal, but that's a different thread). It only makes logical sense that we should be behind at this point. In fact it's pretty amazing that we've come as far as we have. We should be 350+ years behind which we clearly aren't.
Real Amercan scenario:
Black family becomes educated, makes a good living, moves out the hood. There's is no help above them, and they are the help to all those below them. When it comes time to buy a house, they pay more in intrest and loan fees, while still supporting their family that hasn't made it out the hood. It comes time to pay for college, but the parents don't have much cash to throw at it because they are still paying for their own school loans, plus home loans, plus they are still paying off grandmas house. So their kids take out loans of their own and the cycle of debt continues.
On the other hand a white family has support from above. They go to school get the same degree make the same amount of money as the black family, but instead of paying for grandmas house, grandma gives them a house, and mom payed for their schooling, so when it's time to put their kids through school the parents have both the cash and credit to afford it. Grandma sends money for books and living expenses, the kid goes to school without taking out any loans, credit cards, etc, and when he grows up he passes those benefits to his kid.
This is the current dynamic in America and in my opinion only time will fix it. We have been on a constant rise since we were freed as slaves, and we just have to continue at it.
Plus the idea of America being the land of opportunity is totaly false. Upward mobility has been pretty much stagnant for EVERYBODY in America the last 25 years. The wealth gap continues to increase and it has little to do with race at this point.