Ok, so this seems like its been going on for a really long time, and I dont know if I'll anything that hasn't already been said,but Ill try.
So I understand what you're saying. Taking pride in having a some extra melanin, or two X chromosomes is kind of a strange concept on a superficial level. The achievements of other African Americans has nothing to do with me, so why should I be proud? I should be proud of my own actions and want to progress because I want it, not because of some artificial ties to people I know nothing about.
BUT, I think the biggest problem with the logic (not you) is that it ignores the social climate. African Americans have been put down as a group. Told they were ugly as a group. Told they were stupid, cant achieve, were inferior. Black was ugly and useless. People wanted to be something else, anything else to escape that. But to counter that, pride in ones race arose. Black became beautiful and strong and something to be proud of. It was necessarily to take pride in your race, because everyone was telling you it was the worst thing to be. Of course it functioned on an individual level. Individuals were tired of feeling that way, so they took pride in their own hair and skin and features, but that's hard to do alone, when everyone is hating on you. Plus, when you and all your family and friends are being persecuted for the same thing, something that ties you all together and makes you the same, it becomes a group pride. A pride in ones race and culture.
. People have pride in their ethnicity because its not really as superficial as just skin tone. Its not like left hand pride or right hand pride, it comes with serious social implications. Being black was and still carries a slew of challenges. To be proud of a black doctor or physicist or poet is an extension of yourself. You see people struggling like you, making progress and overcoming. They become role models for you and for the future of your race.