Share buybacks can be used for various purposes, and some of those purposes have more of an impact than others.

First - a company may buy back shares to replenish their employee stock remuneration pool. The total number of shares does not change, the value of the shares does not change significantly, and the employees eventually gain that benefit through share issues and discounted stock purchases. This is a valid and important way of cycling some of the companies cash-flow back to employees who gain stock benefits.

Second - a company may buy back shares to replenish or increase their management stock remuneration pool. This may or may not be positive for the company if this is used solely as a way to transfer company liquidity (cash) into the hands of management. This may also change the balance of control in the company from external investors to company management.

Third - a company may buy back stock and cancel the repurchased shares. This increases the value of the existing shares by the proportion of shares cancelled. Lets say the company has 50 million 1$ shares, and buys back 25 million shares and cancels them. The company has spent $25 million dollars, but the value of the remaining 25 million individual shares has increased significantly. They may not have doubled in value (due to the spent capital), but if the company is solid then that value will increase. This is seen as a quick way to again convert company cash into value for significant shareholders (both external investors and management). This approach may also be used to boost value of shares when the company is failing, allowing those in the know to cash out.

As you can see, only one of these approaches benefits company employees, and they do benefit management with significant stock holdings. The cash used for stock buybacks is no longer available for dividends to be paid to external investors - those investors must give up their investment to get a return. I addition, if the company only has significant liquidity due to support that has been provided for pandemic and other economic relief, then that cash being used to benefit management and investors as opposed to employees should be a cause for concern.