Too old for the job and time to make room for the younger generation? Jack Ma thinks so.He’s the CEO of Alibaba Group, the e-commerce conglomerate who said Tuesday he’s stepping down from his post in May. Jack Ma is not even a baby boomer. He’s 48 years old. But he says he’s feeling the strain of his job. “When I was 35, I was so energetic and fresh-thinking, I had nothing to worry about,” Ma said in an interview.