If I understand correctly, you’re asking why “I have a lot of great skills that would really help your company be successful” is ineffective. If that’s correct, it is because he does not list or name any of this skills therefore, the statement is ineffective.
The reason why this sentence is ineffective is because it is a very vague and general statement. In these lines, the author wants to prove that he could be a good addition to a particular company. However, he only talks about his "great skills," but does not specify which skills in particular he refers to, nor provides any evidence for it. Therefore, the sentence is not very persuasive.
The purposes of the two passages are different. The first passage is biographical and contains quotes that reflect Grady's feelings about Reconstruction. The second passage is a personal essay which directly states the author's feelings about Reconstruction.
