Even the highly successful bitcoin investors these days have learned to diversify their investments, which only proves that bitcoin alone is not dependable still.
That applies if you have enough money to invest, but if you're aiming for higher returns, then high-risk investments are the way to go. Some investors still choose to diversify, but they do it within the market itself , for example, they might put 50% of their portfolio in
bitcoin (less risky asset), and then spread the rest across different
altcoins (high-risk assets).