I think that's a perfectly rational statement, in at least some contexts. You could definitely argue that black people in the wealthier western nations are usually likely better off than they'd be if their ancestors had remained in Africa.

I do have a complaint that it sounds like you're thanking existing white people. I, as a white guy, didn't do squat relating to any events before my birth. I could understand thanking my white ancestors for that, or despising them for all the harms they did. I do not understand associating me with those people though.

I think it would be best for society to move away from associating a person's crimes or benevolent actions with their entire race, especially if that person existed long before modern generations.