If there were only a handful of qualified engineers available on the market, then they'd get paid CEO-like salaries due to the value they provide and being in high demand. But because there is a whole market of qualified engineers they get paid far less.

It's pretty basic economics and doesn't have much to do with stock buybacks/dividends/etc... Regardless of the value of an individual position, wages will be lower or higher depending on the supply of an occupation. In the big picture engineers are very replaceable at market price compared to executives so their wages are reflective of that.