Anecdotes are not indicative of overall trends breh. This is the epitome of cherry picking to fit your argument.
The fact of the matter is that there is more black representation in government than ever would have been possible before the CRM. The issue is not the fact we got more representation in the cases you listed, its the inability for the community to hold their representatives feet to the fire by using their votes and putting up candidates to push them out.
Barbara Jordan was the first Black person to be elected to the state senate in Texas since reconstruction due to changes in Civil rights law and was well respected as a congresswoman with her time in the House representing Houston. She was well respected and liked during her time and her ability to become a congresswoman of Houston was directly due to changes in Civil Rights Laws. This is one counter-example I can think of for a place I lived.
To pick a more modern example, you have folks like Cory Booker. I know there are a lot of people here who have some issues with him politically but one thing you could say about him is he geniunely cared about the community he represented and was Mayor for. This is the dude who was offering his personal help with members of the community during hurricane Sandy
Newark's Cory Booker responds personally to citizens' Sandy pleas
Like I said, Cyncism is easy but at the sametime it often is used to oversimplify issues and not deal with the more minute details.