Stock buybacks are basically attempts to shirk leashes, freeing execs/other shareholders from the ongoing influence of exiting shareholders.
Dividends on the other hand, are straightforward returns on what was a commitment to sink risk. An ongoing source of income for the shareholder as a result of the company thriving. It's a straight up payment of a coupon off a bond. There is no need to exit/re-enter required. Your # of shares do not move. Therefore your relative investment stays as it was, whereas with the buyback, you're handing back your ongoing leash and influence on the company.
Stock buybacks are therefore not equivalent in any way to paying of dividends. I don't know why this is so hard to understand.