That argument for stock not being a ponzi scheme is weak.... stock has value because ppl reinvest in it? That's like saying its cold outside because you saw snow on the street
When you buy stock, you buy a partnership in a company. You buy a share in all the equipment and property owned by that company, you buy a share in all goods produced by that company. You don't have to sell the stock to make a profit. You can hold onto it for life and just eat off the dividends. Day trading is just speculation, but there is a hard core of stock owners who don't day trade, and who make their money from the dividends.
Also the more stock you own the greater your control over that company is, so there is an incentive to hold on and even expand your partnership, because that will lead to greater personal control over the company.
Bitcoin isn't like that. You don't own a share of a company. You don't get paid just for holding onto it. You have to sell it to make money.