There's nothing wrong with grouping people based on sharing cultural experiences at around the same age. It's just that the current way of labeling people 1. is rather haphazard and doesn't particularly line up with shared cultural experiences and 2. is completely American-centric. Strictly speaking, boomer/gen x/millennial/zoomer ought to only apply to Americans because non-Americans would have very different shared cultural experiences, which means the demarcation year for each generation would be different. For example, the Chinese equivalent of a boomer would start in 1949 instead of 1945 because 1949 was when the PRC was officially declared and the Chinese Civil War was more or less over. When you experienced the Cultural Revolution would also be a demarcation point as well as 1976, the year when the Cultural Revolution ended.