no. Dividends allow shareholders to receive current cash flow while dividends allow shareholders to receive a potentially higher share price in the future when they sell their shares. Cash today is much more valuable the. Cash tomorrow or otherwise in the future.
Except you can sell your shares today, and receive more money now. Or you can wait for the future and sell then. You choose. There's no opportunity cost lost. Say you own 10% of a company worth $1B. They buyback 10% for $100M, leaving the company worth $900M. Now you own 11.11% of that company, which is worth still $100M. You can now sell 1.11% of the company for $10M, while still owning 10% of the company. Thats the exact same thing that would have happened if they had simply paid a 10% dividend. The only difference is in this case you had the option to not sell that additional 1.11% stake, and defer your taxes.
Logically, there shouldn't be any tax on a company distributing its value to shareholders, in which case this wouldn't matter. But there is, so it does.
You need to remember the NPV of cash today, even if taxed, is still worth more then the NPV of cash years from today, still taxed. An investors income from a stock is going to be taxed regardless, it is just a matter of when, but in both scenarios the profits will be taxed when the investment is turned into cash.
1) Even with a buyback, you can still realize the gains today and have it taxed now, if you want. Its just with dividends, you have to do so, while with buybacks, you get the choice to do that or not.
2) Because tax levels are tiered, the NPV of cash today is not necessarily worth more than the NPV of cash years from today, still taxed. Moreover, if you choose not to sell your increased % share, thereby not collecting your "synthetic dividend", you aren't simply getting delayed cash. You're investing more into the same project. Thus as long as that project continues to generate higher returns than the interest rate, it makes sense to do so. This is why people reinvest dividends sometimes. The difference between this and dividends is that with dividends, if you reinvest, you still get taxed, now. With buybacks, you don't have to be taxed now, since your money is automatically reinvested. You can choose to withdraw that reinvested money by selling shares, but if you do so, you will be taxed. Same as if you had just gotten a dividend.