If Amazon cannot grow, then yes, it's stock price will go down losing you more than you bought the shares for.

stock buybacks are more tax efficient than dividends, but I disagree they are remotely the same thing. There is plenty of empirical evidence that a stock buyback does little to the stock price in the long run, and I would much rather have the decision what to do with the money even though its less tax efficient.

An NFT is a good way to put it.