Earlier quoted context omitted.
" It's like a pyramid scheme in that so long as people keep buying in on the hope of a profit " You just described any investment. FX market, stock market, housing, etc. It doesn't make them "pyramid schemes".
I could buy a bitcoin and hope to sell it later. Or I could buy the S&P 500: a market cap weighted set of pieces of companies that will conduct business and grow by the time I have to sell them, and some will give dividends. Which seems better to you?
Yes, bitcoin benefits from having more people participating in it, but so does Facebook, so does Twitter, so does Youtube, so does the Internet, so does the US dollar, so does the stock market, etc etc etc. That doesn't make these all pyramid schemes.