Buybacks by definition benefit shareholders. They reduce the...

Buybacks by definition benefit shareholders. They reduce the number of shares outstanding, boosting EPS and are a tax effective way of returning capital to shareholders.

I would much rather a buyback than an unfranked (in the case of GAP) dividend if it is done at a sensible price and there are not better capital allocation opportunities. In my experience, most managements tend to make terrible capital allocation decisions. Hence, in my view, the fact that GAP management decided to buyback stock rather than pursue ridiculous acquisitions etc. is a real positive. (Whether the buyback is better option than paying down debt remains to be seen.)

A good book that discusses the topic is The Outsiders by William Thorndike. He points out that buybacks have been a tool used, almost without fault, by the greatest managers in history. Here's an interview with Thorndike in the Harvard Business Review: https://hbr.org/2014/11/when-stock-buybacks-are-not-a-waste-of-money

P.S. Apologies for being obnoxious, I just have rather strong views on the topic.