Money isn’t an investment, it’s a currency. Of course it’s a bad investment and investing in forex is barely a better investment than crypto (purely because there’s less risk of a sovereign currency devaluing to 0).

Investing in capital, like stocks, property, equipment etc does not require someone to lose money for the capital owner to profit. If I invest in a stock, each year I’m paid a dividend based on the profits of that organisation - no losers required. I could later sell that stock at the exact price I paid for it and come away with profit from those dividends. What determines whether it’s a good or bad investment, is the ratio of profit to the capital owner to cost of the asset. Crypto generates 0 profit, so it has 0 value as a capital investment.